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MAYER’S 


WIRELESS TELEGRAPHY AND TELEPHONY: 


A HANDBOOK OF. 


PART 1. 

EMBRACING 


Early Wireless Telegraph—Induction Telegraphy, Etc.—Wireless Telegraph 
Systems, Marconi, Lodge-Muirhead, Slaby-Arco, Telefun ken, 

Singing Spark, Von Lepel, Massie, De Forest, Fessenden, Stone, 
Shoemaker, etc. Amateur Department, etc., etc. 


PART 2. 

EMBRACING 

Light Ray Telephony—Wireless Telephone Systems, Ruhmer, Poulsen, 
De Forest, Telefunken, Fessenden, Collins, Marjorana, etc. 


By WILLIAM MAYER, Jr., 

i ' 

EX-ELECTRICAL, ENGINEER BALTIMORE AND OHIO TELEGRAPH COMPANY; MEMBER 
AMERICAN INSTITUTE ELECTRICAL ENGINEERS; AUTHOR, “AMERICAN 
TELEGRAPHY AND ENCYCLOPEDIA OF THE TELEGRAPH.” 

/ 


366 PAGES 


258 ILLUSTRATIONS. 


) ) 
13 ) 


NEW YORK 

MAVER PUBLISHING COMPANY. 

1910. 





Copyright, 1904—1909, 

By WILLIAM MAYER, Jb. 



< < 

c c 

< ( c 


©CL 4 2 529 81 






PREFACE TO FOURTH EDITION. 

(1910) 


The subject matter of this book was begun several years ago 
'{1901), as an Appendix to the author’s “American Telegraphy and 
Encyclopedia of the Telegraph,” but the rapid progress of the art of 
wireless telegraphy and, subsequently, of wireless telephony, made it 
apparent that a separate book would be required to treat these sub¬ 
jects as fully as was deemed advisable; hence the existence of this 
hand-book. The work having been started along the lines of 
“American Telegraphy,” however, the general plan of that book 
has been followed herein. Consequently, each subject has been 
treated in language as free from mathematical formulae as possible, 
and the whole has been written in a manner designed to be clear to 
the general reader. In the present edition of the book, while 
theory is not by any means neglected, the author has aimed to pay 
particular attention to the practical features of the subject. With 
this end in view practical descriptions of the latest improvements 
in wireless telegraphy and telephony have been added hereto; 
the data relating to which and the accompanying diagrams therefor 
having been obtained in nearly every instance at first hand from the 
engineers or inventors of the systems or devices concerned, to all 
of whom the author hereby acknowledges his great obligations. In 
response to numerous requests an Amateur’s Department has been 
appended to this edition. 

The author is aware that the authorized designation of wireless 
telegraphy and telephony is radio-telegraphy and radio-telephony, 
but for the present has adhered tc the earlier appellations. 

W. M., Jr. 

182 Arlington Avenue, 

Jersey City, N. J. 



PART 1 


* % 
• * « 


CONTENTS 


CHAPTER I. 

PAGE 

Introductory. 1 

Torch, Semaphore, and Other Early Wireless Telegraph Systems. 

CHAPTER II. 

Induction Telegraphy. 6 

Phelps, Edison, Preece, Dolbear Systems. 

CHAPTER III. 

Electric or Hertzian-Wave Telegraphy. 15 

Maxwell’s Electromagnetic Theory of Light—Hertz Experiments— 
Electric Oscillations, etc. 

CHAPTER IV. 

Early Experiments in Electric-Wave Telegraphy. 26 

Branly Coherer—Lodge, Marconi Experiments. 

CHAPTER V. 

Theories of Electric-Wave Propagation—The Elec¬ 
tronic Theory. 29 

CHAPTER VI. 

N 

Syntonic Wireless Telegraphy. 46 

CHAPTER VII. 

Marconi Wireless Telegraph Systems. 52 

Tuned, Untuned, and Long-Distance—Military and Lightship 
Stations—Morse Alphabets, etc. 










VI. 


CONTENTS. 


CHAPTER VIII. 

Lodge and Muirhead Wireless Telegraph Systems. 73 

CHAPTER IX. 

PAGE 

The Slaby-Arco and Braun, Telefunken, Singing Spark, 

Von Lepel, Railway and Portable Wireless Tele¬ 
graph Systems. 87-102 


CHAPTER X. 

The Branly-Popp, Guarini, and Ducretet-Popoff Wire¬ 


less Telegraph Systems. 126 

CHAPTER XI. 

The De Forest Wireless Telegraph System. 135 

CHAPTER XII. 


The Fessenden, Stone, Shoemaker, and Massie Systems.. 149 

CHAPTER XIII. 

Ultra-Violet Rays—Wireless Telephony—Speaking Arc, 

etc..... 172 


CHAPTER XIV. 

Detectors—Interrupters—Transformers—Condensers— 


Aerials—Variometers—Tuning Coils, etc. 182-212 

Tight and Loose Coupling, etc. 

CHAPTER XV. 

Directive Wireless Radiation. 237 


De Forest, Marconi, Braun, Artom, Bellini—Tosi directive 


signaling. 

CHAPTER XVI. 

Practical Applications of Wireless Telegraphy. 250 

CHAPTER XVII. 

Amateur Department. . . 259 

Amateur Wireless Stations, etc. 

APPENDIX. 

Theories—Ehret and Bull Wireless Systems. 291 


Practical Suggestions on Telegraph Signaling, Wave Meters, etc. 












WIRELESS TELEGRAPHY. 


CHAPTER I. 

INTRODUCTORY. 

TORCH, SEMAPHORE, AND OTHER EARLY TELEGRAPH SYSTEMS, ETC. 

Long before the dawn of the Christian era wireless methods of 
communicating intelligence to a distance were employed—not electric 
telegraphs as the term is generally understood, it is true, but wireless 
they certainly were; and as these pages progress it will perhaps not be 
difficult to trace a close relationship, as regards the communicating 
medium employed, between some of the wireless telegraph systems in 
vogue over two thousand years ago, especially those that employed 
the luminiferous ether as the communicating medium, and the wire¬ 
less telegraph systems of to-day. 

The ancient Greeks were probably the first to adopt systematic 
methods of signaling to a distance, and some of the methods which 
they employed have come down to us. One of these is that known 
as the Polybius system, after the historian of that name. A descrip¬ 
tion of this system, which was in use 300 B.c., is to be found in his 
writings. The method employed was as follows: At each station two 
walls about ten feet in length and about six feet high were built. 
These walls were separated by a space of about ten feet. At night 
torches were placed on the top of the walls, one or more torches on 
each wall, and certain combinations of the torches represented the 
letters of the Greek alphabet. A tablet showing the letters of the 
alphabet, as indicated in Fig. 1, was provided at each station. The 
torches placed on the right-hand wall represented the vertical row of 



WIRELESS TELEGRAPHY. 


figures; those on the left wall, the horizontal row of figures. There 
were in all five torches on each side. In the figure the English alpha¬ 
bet is used for convenience. Using this code, the letter M would be 
signaled by placing three torches side by side on each wall; the 
letter H would be indicated by two torches on the right-hand wall 
and three on the left, as in the figure, and so on, the letters being 
found at the point of intersection of the horizontal and vertical rows 
of figures on the tablet. In order to distinguish accurately between 



Fig. 1. Polybius Telegraph. 


the two sets of torches, since at night the walls were not visible, a 
double tube was employed, and was so arranged that when the attend¬ 
ant looked through both tubes at once he saw both sets of torches; 
but when he looked through one tube he saw only one set, which 
insured a correct vision of the combination. When not in use for 
signaling, the torches were placed behind the walls. When it was 
desired to “call” a distant station, two torches were set on a wall 
and the call was answered by a similar signal. 

It may be noted that the code here shown is, in a more or less 
modified form, in use to-day by the military departments of various 
countries as a means of telegraphing maps. For this purpose the 
map is drawn on a sheet of properly squared paper, of which there 
are duplicates at each station. The outlines of the map are indicated 
by sending, in a prearranged way, the numbered vertical and hori¬ 
zontal rows of squares intersected by the lines of the map. 
























































SEMAPHORE TELEGRAPHY. 


3 


The Gauls, also, were wont to transmit intelligence of importance 
to a distance by a cruder and simpler, if not as efficient, method. 
A messenger was despatched to a hillside, where he shouted or trum¬ 
peted his message apparently to the winds. Soon from afar a voice 
or trumpet answered him and repeated the message to another listener 
farther on, and thus from one point to another the message sped; and 
it is recorded that in this way a message calling all the tribes of Gauls 
to arms traveled in three days from Auvergne to the forests of Amorica 
in one direction and to the banks of the Rhine in another. 

With perhaps a few exceptions, also, methods of transmitting 
intelligence to a distance have been and are practised by even the 
most uncivilized races. The use of fires by night and smoke by 
day as a means of communicating the whereabouts of an enemy, or 
other intelligence, has long been practised by various Indian tribes in 
this country. In the Cameroon country, Africa, the tribes employ 
an instrument which they term the elliembec, on which they tap, by 
some form of phonetic code known only to themselves, signals from 
one point to another in the densest forests, and up and down the 
rivers of that country. The elliembec is a sort of drum of cylindrical 
shape, about three feet long and six inches in diameter, having 
holes in the sides and in the end, through which the sound passes. 
According to Garner, messages are transmitted from town to town as 
far as three miles apart by means of this instrument. 

Toward the close of the eighteenth century another wireless tele¬ 
graph system, the semaphore, was invented by a Frenchman, Claude 
Chappie. The Chappe semaphore, like the signaling devices so com¬ 
monly used on railroads to-day, consisted of an upright post, on the 
top of which movable arms were pivoted. In the Chappe semaphore, 
however, the arms were arranged quite differently from the ordinary 
railroad semaphore. Thus, the cross-arm on the top of the post was 
about fourteen feet in length; at each end of this long arm a shorter 
arm was pivoted. By a system of pulleys and ropes these arms could 
be placed in a great many different positions, and certain positions 
were allotted to the different letters of the alphabet. A miniature of 
the semaphore arms, operated also by the ropes and pulleys, was 
placed at the bottom of the post, by means of which the operator 
could see the position in which he was placing the arms. 

These semaphores (Fig. 2) were placed on towers, hills, etc., six 
or ten miles apart, and expert operators could signal at the rate of 


4 


WIRELESS TELEGRAPHY. 


about three words per minute. To enable the operators to observe 
the distant signals telescopes were placed in every tower. This 
method of telegraphing was widely introduced in Europe, especially 

in France and Russia, and by repeating 
the signals from tower to tower, territory 
covering hundreds of miles was brought 
within signaling distance. In Russia 
alone a string of these towers extended 
from the Prussian frontier to St. Peters¬ 
burg, a distance of over 1200 miles. 

Other wireless telegraph s} r stems, iir 
the strict sense of the word, are the well- 
known heliograph or mirror signaling sys¬ 
tems, flash-light signaling, wig-wagging, 
torch signaling, etc., now in general use 
by the various army and navy signal corps 
of the world, and may be found described 
in the author’s work “American Teleg¬ 
raphy.” 

After the semaphore system came the 
Fig. 2. Chappe Semaphore, electric wire telegraph, and after that the 

electric wireless telegraph systems. In 
fact, it may be noted, contrary to the popular view, that electric wire¬ 
less telegraphy was practised in a small way before the invention of 
wire telegraphy. Thus, over one hundred and fifty years ago electric 
signals were sent without wires through water, across rivers, lakes, 
etc. For example, Dr. 


Watson, Bishop of Llan- 
daff, sent electric shocks 
across the Thames, and 
subsequently throng h 
the New River at New¬ 
ington. Similar experi¬ 
ments were made by 

Franklin in 1748 across the Schuylkill at Philadelphia, and by Du 
Luc a year later across the Lake of Geneva. Morse also, in 1842, 
transmitted signals across a canal eighty feet wide without wires, using 
the arrangement shown in Fig. 3, in which w w are insulated wires 
200 to 400 feet in length; G is a galvanometer; the battery is shown 




Fig. 3. Telegraphing through Water. 























SIGNALING THROUGH WATER. 


5 


by vertical thick and thin dashes; c c are large copper plates about 
five feet long by two feet wide. A key was used to open and close the 
battery circuit. Similar experiments, but on a larger scale, in India 
and elsewhere have shown that the best results are obtained when the 
length of the wires on the shore is equal to the width of the river to 
be signaled over. But in all of these instances the water or earth was 
the conductor of the electric impulses or current. 

It is evident that the systems just referred to are not wireless in 
any other sense than that named, for, in the instruments used, and 
outside of them, wires are still very much in evidence. The term is, 
however, a convenient one, and indicates clearly enough what is meant, 
namely, the absence of a connecting wire between stations, and more 
especially so when it is considered how absolutely necessary the con¬ 
necting wire between stations of an electric telegraph system was at 
one time thought to be. Scarcely a writer on the subject of electric 
telegraphy forty or fifty years ago but felt bound to sing its praises. 
Thus, 

“ From clime to clime, from shore to shore, 

Shall thrill the magic thread; 

The new Prometheus steals once more 
The fire that wakes the dead.” 

The term “ wireless telegraphy ” as now generally used, however, 
refers to the more recently devised electrical wireless methods, like 
Marconi’s, De Forest’s, etc., in which the wire between the transmit¬ 
ting and receiving stations is dispensed with, and in which electric 
or ether waves in free space are utilized between the sending and 
receiving stations. These, however, are not the only wireless tele¬ 
graph systems in which electric waves are the important factor, for it 
is well known that during the past fifteen or eighteen years there have 
been in limited use a number of wireless electric telegraph systems, 
which have been sometimes called, perhaps for want of a more apt 
name, induction telegraph systems, some of which will be described. 

The following are some of the other terms that have been suggested 
for the new telegraphy: space telegraphy, spark telegraphy, teleg¬ 
raphy without line wires, electric-wave telegraphy, ethereal-wave 
telegraphy, and Hertzian-wave telegraphy. In general, however, the 
term “wireless telegraphy” will be used in the following pages to 
denote electric-wave or Hertzian-wave telegraphy. 


CHAPTER II. 


INDUCTION TELEGRAPHY. 


PHELPS, EDISON, PREECE, DOLBEAR SYSTEMS. 

Electromagnetic and electrostatic induction systems are based 
on the phenomena of mutual induction between wires. Electromag¬ 
netic induction was discovered by Faraday and Henry. Henry’s 
experiments were chiefly with flat coils of wire, one placed above 
another. When a circuit containing such a coil and a battery was 
opened and closed, it was noticed that a current was induced in the 
neighboring wire, which current was in the opposite direction to that 
of the originating current. This current would be indicated by a 
galvanometer in the second circuit. This action may also take place 
between two straight parallel wires. In Fig. 4, for example, let A 
and b be two parallel circuits; b the source of electromotive force. 

If the key k be opened 


and closed at intervals, 
it will be seen by the 
deflections of the gal¬ 
vanometer G that cur¬ 
rents are at such times 
set up in b, and that 



x 




Fig. 4. 


the current set up when the key is closed is opposite to that originated 
when the key is opened; and, further, that the current originated in 
b at the closing is opposite in direction to that of the current due to 
battery b, and vice versa. 

This effect is explained by saying that the magnetic lines of force 
which surround a wire conveying a current, in rising and falling 
“cut” the parallel wire and induce in it currents which vary in 
strength and frequency with the current in the first wire. If the 
wires a and b are made sufficiently long and a sufficiently high electro¬ 
motive force be employed, and the circuit be made and broken quickly 
in one of the wires, induced currents will be indicated in the second 















THE INDUCTION COIL. 


7 


wire, even when the wires have been widely separated. This fact is 
utilized in the Phelps, Preece, and other induction telegraph systems. 

Electrostatic induction is explained by tiie fact that when a metal 
plate, wire, or other conductor of electricity receives a charge of 
positive or negative electricity it induces in a neighboring conductor 
a charge of opposite polarity. In the act of taking this charge, and 
also when the charge is dissipated, a momentary current is set up in 
the conductor. But in the case of static induction the current set 
up in the neighboring conductor, for example, b, Fig. 4, is in prac¬ 
tically the same direction as that accompanying the currents of charge 
and discharge in wire A. (See pp. 25, 31.) 

The Induction Coil.—This piece of apparatus, which is used exten¬ 
sively in wireless telegraphy, X-ray work, etc., is designed to avail of 
the mutual induction between parallel wires. The turns of the first 
or primary wire or coil (see c, Fig. 6) is wound over a core of small 
iron wires; the secondary wire or coil is also wound over this core, 
either side by side with, or above, the primary wire. The turns 
of the primary wire, in which the battery is placed, being adjacent 
to the turns of the secondary wire, the makes and breaks of the 
circuit, or rapid variations, however produced, in the strength of 
current in the primary circuit, set up currents of alternating polarity 
in the secondary coil. The number of turns in the primary wire of 
an induction coil are comparatively few, and the wire used is coarse; 
while the secondary wire is composed of many turns of a fine wire. 
The number of convolutions in the primary of an induction coil used 
in telephony may be 61, with a resistance of .25 ohm; the number of 
convolutions of the secondary 1950, resistance 100 ohms. In the 
larger induction coils, giving, for instance, a ten-inch spark, the resist¬ 
ance of the primary may be .3 ohm; that of the secondary, 12,000 
ohms. The electromotive force developed in a circuit is proportional 
to the lines of force cutting the circuit in a given time. Hence, as 
the lines of force of the primary wire in rising and falling cut each 
turn of the secondary wire separately, the total electromotive force in 
the latter is amplified manifold, while, of course, the current is 
reduced, owing to the high resistance of the secondary wire. The 
strength of an induction coil is usually signified by the length of spark 
it will give through air, between the terminals of the secondary wire. 

In the smaller sizes of induction coils the makes and breaks of the 
primary circuit are usually obtained by a device similar to that of the 


8 


WIRELESS TELEGRAPHY. 


“buzzer” or ordinary electric door-bell, as at B, Fig. G, which is 
termed the interrupter or vibrator. A condenser is generally placed 
across the contact points of the vibrator, it having been found that 
this adds largely to the efficiency of the coil and diminishes sparking 
at the contacts. The electric condenser is virtually a Leyden jar 
arranged in a convenient form, usually consisting of sheets of tin-foil 
separated by paraffin paper or mica, the alternate sheets of tin-foil 
being connected together, making two series of sheets. The size of 
induction coils used .in wireless telegraphy for setting up electric 
oscillations in the transmitting circuit varies from a few inches in 



Fig. 5. Induction Coil. 

length and diameter to over a foot in length and eight inches in 
diameter, depending on the length of spark or power desired. The 
general external appearance of a fairly large induction coil is illus¬ 
trated in Fig. 5. In coils of this size the vibrator is usually separate 
from the coil, owing to the rapid disintegration of the contacts at B 
under a heavy current. The vibrator in Fig, 5 is a magnetic interrupter. 
It is shown at the right of figure. The condenser is contained in the 
square box shown to left of the interrupter. The capacity of the 
condenser is va io 1 by the handle on top of box. The switches shown 
are for opening and reversing battery as desired. Other forms of 
interrupters are also used in the primary of the induction coil. Some 
of these interrupters consist of devices by which the primary cir- 











PHELPS INDUCTION TELEGRAPH. 


9 


euit is broken mechanically, as in the Preece system. In others the 
primary circuit is broken by lowering and raising contacts in and out 
of cups containing mercury, and by other means, some of the devices 
for which will be described and illustrated in a subsequent chapter. 
(See Index.) 

For practical purposes it may be assumed that there is but 
one “rise” and one “fall” of the lines of force of the secondary 
circuit for each make and each break of the primary of the induction 
coil. For, while certain experiments of Bernstein and others have 
shown that there are surgings or oscillations of the current between 
the interruptions of the battery current, the extra pulsations are sc 
quickly dampened their effect is not markedly appreciable. Further 
reference to electric oscillations will be made in connection with the 
subject of Hertzian waves. 

THE PHELPS INDUCTION TELEGRAPH. 

This was perhaps the first induction telegraph system put into 
practical operation either in this country or in Europe. It was 



Fig. 6. Phelps Induction Telegraph 


devised in 1886 as a means of communicating between a moving train 
and railroad stations. The arrangement of the apparatus and cir¬ 
cuits employed is shown in Fig. 6. An insulated wire w is laid be¬ 
tween the rails of the track from station to station. A coil of wire 
c is wound in a suitable frame around the car, as shown by the black 
lines, the car itself being indicated by the dotted lines. An induc¬ 
tion coil I is used to set up pulsations in the coil, which pulsations, 
by electromagnetic induction, are transmitted through the air to the 
wire w between the rails. A similar arrangement of induction coil, 
key, and telephone to that shown in the car is employed at the station. 
The pulsations thus developed in the wire w are heard in the tele- 































10 


WIRELESS TELEGRAPHY. 


phone at the station as a prolonged tone or “buzz” when the key or 
transmitter k is closed, but when the key is opened the tone ceases, 
as at such times the secondary coil c' is open. Then, by opening and 
closing the key k, long and short tones, corresponding to the dots 
and dashes of the Morse alphabet, may be transmitted by the operator 
in the car and received by the operator in the station. In like 
manner the induction coil in the station may be set in operation 
and the pulsations traversing the wire between the rails will induce 
pulsatory currents in the coil around the car, which pulsations may 
also be similarly broken into dots and dashes by the operator at the 
station and received as intelligible signals by the attendant in the car. 
It may be seen that the connections of the coil and telephone T are 
arranged so that when the transmitter is open the telephone is placed 
in the circuit, while the induction coil c' is out of circuit, and when 
the key is closed, as in the figure, the reverse is the case. In the fig¬ 
ure, b is the armature or interrupter of the primary circuit of the induc¬ 
tion coil. For clearness, the respective coils of the induction coil are 
placed end to end over the core of iron wires. This system was in use 
on a twelve- or fifteen-mile section of one of the railroads running 
out of New York, and the writer had several opportunities to observe 
it in actual operation. Morse signals, composed, as stated, of long 
and short tones in the telephone, were readily interchanged between 
stations and the car throughout the continuance of the trips. Even 
when the car equipped with the coil and apparatus was switched off 
to a side-track sixty feet from the track wire, it was quite possible to 
exchange messages with the car and station. 

THE EDISON INDUCTION TELEGRAPH. 

Another induction telegraph system, shown in Fig. 7, somewhat 
similar to the one just described, so far as the arrangement of the 
transmitting and receiving apparatus in the station and car is con¬ 
cerned, was also in actual operation for a similar purpose on the Lehigh 
Valley Railroad. This was an electrostatic induction system, and was 
devised by Wiley Smith in 1881. Later it was improved by Edison 
and Gilliland. 

In this system the metallic roofing Y of the car or cars of the train 
is used as one large plate of a condenser; the telegraph wires by the 
side of the track as the other plate; the insulating medium or di¬ 
electric being the intervening air. At the station x several ordinary 


PREECE INDUCTION TELEGRAPH. 


11 


condensers are connected by one terminal to adjacent telegraph wires, 
while their other terminal is connected to the transmitter or key and 
thence through the apparatus to ground. In the car the metallic 
roofing is connected to the key and thence through the induction coil 
or telephone to ground. In this system, when the induction coil at 
either station is operated the condensers in the one case and the roofs 
and adjacent wires in the other are alternately charged and dis¬ 
charged; the currents thus produced setting up in the telephone at 



Fig. 7. Edison Induction Telegraphy. 


the receiving station a tone practically similar to that set up by the 
operation of the induction coil in the magnetic method. 

When these systems were first introduced it was assumed that a 
general demand would arise for them on all railroads, the advocates 
of the system urging that they would afford a means of preventing 
accidents, collisions especially, and incidentally would keep travelers 
in continuous connection with the “ stationary ” world. The expec¬ 
tations in this respect, however, were not realized. 

THE PREECE ELECTROMAGNETIC METHOD. 

By an analogous method to that of the Phelps induction system, 
namely, the electromagnetic method, Sir W. H. Preece in 1892 suc¬ 
ceeded in signaling to a distance of over three miles without inter¬ 
vening wires, between Penarth on the mainland, and the island of 
Plat Holm in the Bristol Channel. Two parallel wires on poles were 












































































12 


WIRELESS TELEGRAPHY. 


nsed, one on the mainland, the other on the island. The wires were 
from one to three miles in length. These wires served alternately 
afc the primary or secondary wires, depending on which was employed 
as the transmitting or receiving wire. The respective wires were 
grounded at each end. Telephones were used as the receivers, as in 
the Phelps and Edison systems. 

Instead of an induction coil to set up the electromagnetic im¬ 
pulses, Mr. Preece employed a motor-driven make-and-break wheel b 
(Fig. 8), by which means a sharper rise and fall of current is ob¬ 
tained, which in turn has a more pronounced effect upon the receiv- 


—MWIr 




ins' instrument t. The break-wheel is shunted by a condenser c; 
r is an adjustable resistance. Battery b consists of about 100 
dry cells. About 600 alternations per second were used. Mr. 

Preece states that the 
100 cells with this break- 
wheel give as good results 
at 3.3 miles as 21 horse¬ 
power transformed into 
alternating currents by 
a transformer, or induc- 

Fig. 8. Preece Induction Telegraph (Theory). ^ on co ^’ owing to the 

smoother sinusoidal 

curves of the latter. When key k is closed the pulsations from B 
are transmitted to the line; when open, the telephone t is in circuit 
for receiving signals from the distant station. 

More recently the same experimenter has succeeded in establish¬ 
ing a wireless telephone circuit by means of which speech is trans¬ 
mitted between the Skerries lightship and the mainland of Anglesey, 
a distance of nearly three miles; the parallel wire on the Skerries 
Islands being 750 yards in length, and that on the mainland 3.5 miles 
in length, the ends of each wire terminating in the sea. On these 
systems both magnetic induction and electric conduction through the 
earth and water are utilized. The ordinary telephone transmitter and 
receiver are employed. It was suggested that vessels could hold speech 
with one another, by this arrangement, a considerable distance apart, 
by having a copper wire carried from bow to stern and passing over 
the topmast, the ends of the wire being in the sea. 

Evershed Calling Relay.— In the Phelps induction system it 
was at first attempted to operate a relay by the induced pulsations of 
current and cause the relay to operate a sounder, in order that the 











EVERSHED CALLING RELAY. 


13 


usual Morse method of receiving might be employed. Such a plan 
would also afford ail audible method of calling a station. This ar¬ 
rangement was not, however, very satisfactory, and the telephone as a 
receiver was utilized. It will be obvious that in the latter case it is 
necessary that the attendant should keep the telephone constantly at 
his ear to be ready to acknowledge calls. In the Preece system this 
difficulty has been met by the use of a sensitive relay, due to Mr. S. 
Evershed. This relay consists of a rectangle of very fine wire, the free 
end of which is placed in the field of a strong magnet. The rectangle 
is supported at its fixed end by an insulating block. The wire form¬ 
ing the rectangle is made a part of the signaling circuit. When an 
alternating current is set up in the rectangle its free end vibrates up 
and down, due to the mutual effect of the field of the magnet and the 
magnetic field thus set up in the fine wire. A contact screw, or 
point, controlling the local circuit of a call-bell, is placed in such 
proximity to the free end of the rectangle that the local circuit is 
closed when the rectangle vibrates, by which means the call-bell is 
■operated. A modification of this relay was also devised by Mr. Ever- 
shed, in which two rectangles are so placed that contact points at¬ 
tached to their free ends come together and close a local circuit when 
the magnetic pulsations traverse the receiving circuit. The connec¬ 
tions of the respective coils are such that the pulsations cause them 
to oscillate in opposite phases, and the local contact points are so ar¬ 
ranged that they close the local circuit at such times. When, on the 
other hand, the coils are mechanically shaken, they vibrate in unison 
and the contacts do not close the circuit. The advantage of this is 
that the jarring, etc., to which such instruments are liable on shipboard 
do not cause false “calls.” The fundamental rate of vibration of 
these rectangles is sixteen periods per second. The method employed for 
setting up the calling pulsations is as follows: A small alternator, to 
the armature-shaft of which a heavy fly-wheel is attached, is set in 
operation by hand. It is first caused to revolve at a higher rate than 
necessary to set up pulsations of sixteen periods per second, whereupon 
“ the exciting current is switched on and the machine is allowed to 
■come gradually to rest, passing slowly through the synchronizing 
speed, so that the two rectangles have time to come to their maximum 
amplitude,” and the call is given. 

In these systems it lias been found that the length of the parallel 
wires should be equal to the distance to be signaled across, as in the 
•case cited of signaling through water. 


14 


WIRELESS TELEGRAPHY. 


Stevenson’s Experiments. —Many experiments on a large scale 
have been made with coils of wire as a means of signaling by electro¬ 
magnetic induction. In some of the experiments the coil has been in 
the shape of a ring, in others a triangle, rectangle, etc. As a result 
of some of these experiments Mr. C. A. Stevenson found that to 
signal across half a mile, nine turns of No. 8 iron wire, forming a 
coil 400 feet in diameter, and a current of one ampere, were requisite. 
Mr. Stevenson points out that the signaling distance by this method 
“is proportional to the square root of the diameter of one of the coils, 
so that with any given number of turns, to signal double the distance 
requires double the diameter of the coils, or double the number of 
turns. But this law does not hold when the coils are close together.” 

In other experiments, two coils, each 600 feet in diameter, and 
separated by a space of about 2550 feet, from center to center, were 
employed, and signals were easily received by the use of two tele¬ 
phones. A battery of 100 dry cells was used, but signals could still 
be read when the battery was cut down to 15 cells. The effect of 
putting the terminals of the coils to ground was tested as compared 
with the results when a complete metallic circuit was employed, and 
but little difference was noted. 


In 1886 Mr. A. E. Dolbear patented a wireless telegraph system 
consisting of a vertical wire at each station, with means for establish¬ 
ing a positive potential at one ground and a negative at another, when 
by varying the potential at one ground the potential at the other 
ground would be varied, which variations, by causing currents to 
traverse the earth between the stations, would operate a telephone 
receiver. Mr. Dolbear experimented with these devices, using a kite 
to uphold the vertical wires, and was able to receive telegraph signals 
over short distances. (U. S. Patent, No. 350,299.) 

In 1891 Mr.T. A. Edison patented an induction telegraph system 
designed for communicating between land stations and between ves¬ 
sels at sea. He also proposed to use vertical wires supported by the 
masts of ships or by captive balloons. He proposed to use an induc¬ 
tion coil to set up rapid pulsations at the transmitting station, and a 
sensitive receiving instrument, such as a telephone receiver, at the 
receiving station. (U. S. Patent, No. 465,971.) 

Mr. Edison’s view was that the electrostatic impulses set up 
would be transmitted inductively through the intervening air. 



CHAPTER III. 


ELECTRIC OR HERTZIAN-WAVE TELEGRAPHY. 

MAXWELl/S ELECTROMAGNETIC THEORY OF LIGHT—HERTZ EXPERI¬ 
MENTS—ELECTRIC OSCILLATIONS, ETC. 

It is not conceivable that action of any kind can take place at 
a distance without the aid of some intervening medium. When the 
old-fashioned door-bells were in vogue, the visible medium between 
the bell-pull at the door and the bell within the house was the wire 
with its crank-levers; the ringing of the church-bell in the belfry is 
accounted for by the connecting rope leading down to the sexton; 
and the fact that a voice, bell, or tuning-fork is heard across a com¬ 
paratively short space is accounted for by the theory of the propaga¬ 
tion of sound-waves in air. 

The explanation of the manner in which this sound reaches the 
ear is that the voice, bell, or fork sets the surrounding air-particles 
into to-and-fro vibrations or excursions, which vibrations or waves are 
propagated from particle to particle of air, or from one series of par¬ 
ticles to another series, in every direction radially from the source. 
In each full wave there are two condensations and two rarefactions of 
the air-particles. When the air-waves reach the drum of the ear the 
latter is set into corresponding vibration and the sensation of sound 
is produced. Sound-waves are thus said to oscillate longitudinally to 
the direction of propagation. 

That the air is the medium by which sound is transmitted in the 
cases mentioned, may be demonstrated by the familiar experiment with 
a bell in an air-chamber from which it is possible to remove the air. 
An electric bell may be started ringing in the chamber, through the 
glass sides of which the bell may be seen and heard. When the air- 
pump is set in operation and the chamber is gradually exhausted of 
its air, the sound of the bell fades away and at last dies out, notwith¬ 
standing that its clapper is still to be seen in full operation; thus 


16 


WIRELESS TELEGRAPHY. 


proving that the air was the medium by which the sound of the bell 1 
was propagated to us. As just remarked, however, the bell is still 
visible. Evidently, then, since the idea of action at a distance with¬ 
out a connecting medium has been disavowed, the medium by which 
we see the bell has not been removed. Inasmuch as the air is not the- 
medium by which the vibrating bell (or anything else) is visible to 
us, it is apparent that another medium exists by which light is propa¬ 
gated, a point which is still more obvious when it is considered that 
the atmosphere does not extend a thousand miles, at most, beyond the- 
earth, and yet the light of the most distant visible stars reaches us. 
This medium is termed the ether, a substance which apparently per¬ 
vades all space and all bodies, and to which the glass sides or walls of 
the air-chamber in the experiment referred to are as open as would 
be a bird-cage placed in a pond to the water, and vastly more so. 
Dr. Lodge has thus defined this medium: “The ether is a perfectly 
continuous, subtle, incompressible substance, pervading all space and 
penetrating between the molecules of all ordinary matter, which are 
imbedded in it and connected with one another by its means. And. 
we must regard it as the one universal medium by which all actions 
between bodies are carried on; its function is to act as the transmitter 
of motion and energy.” 

It is assumed that the propagation of sound-waves in air, and also 
some of the phenomena connected therewith, are in some respects 
analogous to the propagation of light-waves in the ether. It will, 
perhaps, therefore be of service to touch briefly upon some of the- 
known facts in connection with the more familiar subject, sound-waves. 

When a tuning-fork is struck while held by its handle it vibrates 
at a given rate, depending upon the length, diameter, etc., of the- 
fork; and, in doing so, gives out a sound or note of a certain pitch, 
which is termed its fundamental note. In transmitting sound air- 
waves travel at the rate of about 1120 feet per second (the speed or 
velocity varies somewhat with temperature). From this it follows 
that the length of a wave will depend upon the number of vibrations 
per second. Hence, if to produce the note c 261 to-and-fro vibra¬ 
tions or oscillations are required, the wave-length of that note will 
be -VV 2 t> °L roughly, 4-3 feet. For the octave of that note the vibra¬ 
tions would be double, that is, 522 per second, and its wave-length 
will therefore be halved. 

When the fundamental rate of vibration of forks, reeds, strings,. 


LIC4HT VIBRATIONS. 


17 

etc., is the same they are said to be in unison, harmony, or syn- 
tony. When thus attuned, such forks or strings readily respond to 
sound-vibrations of their own rate, and continue to vibrate for a time 
after the originating cause has ceased. For example, if a tuning-fork 
is set in vibration adjacent to another exactly similar fork, the latter 
will presently begin to vibrate in response to the air-vibrations set up 
by the first fork, and will continue to vibrate for some time after the 
first fork is removed. But vibrations or waves of a different order, 
unless they be harmonics or octaves of the fundamental note, will not 
materially affect the forks. Fortunately, such things as the ear-drum 
and the diaphragm of a telephone receiver are quickly responsive to a 
large variety of vibrations and come to rest or are dampened practi¬ 
cally concurrently with the originating cause of the vibrations. It is 
well known that sound-waves are reflected from an object which they 
cannot penetrate, giving rise thereby to the familiar echo. It is also 
known that sound-waves are refrangible; that is, they change their 
direction in passing from one medium to another, etc. 

According to the undulatory theory of light, the atoms or mole¬ 
cules of a luminous body, such as an ordinary lamp, vibrate with ex¬ 
ceeding rapidity, and these vibrations are communicated to the ether 
within and surrounding the luminous body, and thereby correspond¬ 
ing disturbances, vibrations, or undulations are set up in the ether, 
which radiate in every direction from the source. These waves or 
undulations in the ether when they reach the eye give lise to the sen¬ 
sation of light. Experiments and calculations have shown that light 
travels at the rate of about 186,000 miles per second. Also that the 
light-waves which when they fall upon the letina aie manifested as 
red light, vibrate at the rate of about 400,000,000,000,000 per second; 
the waves that produce violet light, at the i ate of 700,000,000,000,000 
per second; while the undulations that pioduce yellow, blue, oiange, 
etc., fall between those figures; and the combination of all these dif¬ 
ferent undulations gives white or day light. The length of these 
waves is exceedingly small, about -g-yoVcT iec l light and ygroir 

inch for violet light. It has long been known that the luminiferous 
waves, like other forms of wave motion, can be reflected, refiacted, etc. 

In 1864 Clerk-Maxwell demonstrated mathematically the electro¬ 
magnetic theory of light, which, in effect, is, that electromagnetic 
manifestations are due to undulations of the all-pervading ether, of 
a more or less similar nature to the undulations which produce the 



18 


WIRELESS TELEGRAPHY. 


manifestations of light, and that in so far as they differ it is mainly a 
difference in degree as to the number of vibrations per second, the 
electric undulations of the ether varying from a few hundreds or 
thousands to many millions. In other words, it is a difference in the 
wave-length of the respective undulations. Further, the theory 
showed that light and electricity travel in free space at a correspond¬ 
ing speed. 

Gordon states Clerk-Maxwell’s electromagnetic theory of light 
thus: “Electromagnetic induction is propagated through space by 
strains or vibrations of the same ether which conveys the light-vibra¬ 
tions; or, in other words, light itself is an electromagnetic disturb¬ 
ance. . . . The chief point of resemblance between the modes of 
propagation of light and electromagnetic induction is that in both 
cases it can be shown mathematically that the disturbance is at right 
angles to the direction of propagation. It is known that the waves 
of light take place in directions at right angles to the ray. Maxwell 
has shown that the directions of both the magnetic and electric dis¬ 
turbances are also at right angles to the line of force. They are also 
at right angles to each other/’ 

Following Clerk-Maxwell’s announcement of his electromagnetic 
theory of light, which involved the existence of electric waves in free 
space, many physicists set themselves the task of demonstrating by 
experiment the truth of this theory. It was not, however, until 1887 
that the actual existence of electric waves in free space was demon¬ 
strated, the great honor of this accomplishment falling to Prof. H. 
Hertz, some of whose experiments will be described shortly. 

It was first shown by Lord Kelvin, in 1853, that when a Leyden 
jar or other highly insulated condenser is discharged, the previous 
charge is not dissipated at one rush, but gradually, in a series of os¬ 
cillations. A mechanical analogy of this oscillatory action may be 
offered. Assume the bob of a pendulum or a ball, upheld by a string, 
to be raised to a certain point above its zero. By reason of its posi¬ 
tion the ball now possesses a certain potential energy, or power to do 
work, due in this case to gravity, the work having been done against 
gravity in raising the ball to its present position. When the ball is 
allowed to fall it descends and at once begins to give up its potential 
energy, but as it does so it acquires kinetic energy, or energy of motion 
(due to that property of matter termed inertia, by virtue of which 


OSCILLATIONS. 


19 


matter tends to continue at rest when at rest and to continue in motion 
when in motion), which carries it past the lowest or zero point, and 
on in the opposite direction. As the ball ascends it now gives up its 
kinetic energy, but is again acquiring potential energy. If there 
were no friction of the air, or of any other kind, to be overcome, 
the ball would rise to a point equal to that from which it had started, 
and would then reverse its direction and return to zero, acquiring as 
it fell kinetic energy, which would carry it back to its original start¬ 
ing-point, and it would thus oscillate indefinitely. But as friction 
cannot be wholly eliminated, it is evident that the amplitude of the 
oscillations would gradually shorten and the ball would come to rest 
at zero after a few oscillations, depending upon the amount of the 
friction, the height to which it had been raised originally, etc. If, 
further, the ball should be moved in some viscous substance, it is 
clear that it might slowly descend to the zero point and come to rest 
there without oscillating, the potential energy having been used up 
in overcoming the resistance of the viscous substance. 

It is well known that in an electric circuit containing coils of 
wire or magnets the current is retarded in rising and falling, which 
fact is due to the property termed self-induction, or inductance. On 
the contrary, when a wire possesses static capacity the current is assisted 
in rising and accelerated in falling. The property of inductance is 
usually likened to inertia, while capacity is likened to elasticity, 
in mechanics. 

Inductance is that property of a circuit upon which depends the 
number of self-induced magnetic lines of force that will be set up 
around the circuit when the current in the circuit is varying. Capac¬ 
ity is that property of a circuit upon which depends the amount of 
charge the circuit will acquire with a given electromotive force; it 
might be termed the electricity-holding quality of a circuit. Resist¬ 
ance may be considered the molecular friction which theE. M. F. must 
overcome in forcing the current through the conductor. In a circuit 
that contains no magnetic material such as iron within or surrounding 
it, the inductance of the circuit is constant regardless of the strength 
of current. The capacity of a given circuit is also constant, as is also 
the resistance of a circuit if a uniform temperature of the conductor 
be maintained. 

In setting up the magnetic lines of force (that accompany an elec- 


20 


WIRELESS TELEGRAPHY. 


trie current) in the medium or dielectric surrounding a circuit, a 
certain amount of energy is expended (and the starting of the current 
is retarded), but this energy is returned to the circuit as kinetic energy 
when the circuit is broken or when the current strength is decreased. 
In setting up the stress in the medium or dielectric surrounding a 
conductor having capacity, a certain amount of potential energy is 
stored, which is returned to the circuit as kinetic energy when the 
stress or pressure is decreased. In both cases, therefore, the energy 
of inductance and capacity is returned to the circuit practically as in. 
the mechanical analogy cited. The electrical energy expended in 
overcoming the resistance of the circuit, however, is not returned to 
the circuit, but is dissipated in heating the conductor. 

A charged condenser or conductor has acquired a potential energy 
due to the work done in charging it, which work is equal to £qe. 
ergs, or units of work, when E is the potential to or through which 
the electricity has been raised or displaced from zero, and q is the 
charge; Q being equal to the product of E by the capacity of the con¬ 
denser, k. As the potential starts from zero, the total work done is 
the average of the total potentials during the time that the electricity 
is being raised to maximum, which average it is known is one half of 
the maximum potential, namely, |e, and hence the total work is 4q,e. 

The foregoing is more frequently stated as follows: Potential 

Q 2 

energy = ■£— ergs; which latter statement is the equivalent of the 
other and is derived by simple substitution of terms. Thus, if Q = ke, 

Q Q 2 Q 2 

then -— = e and — = qe. Hence, 4qe = A—. 

K K “ K 

Taking a numerical example: 

If Q = 12, k — 3, and E = 4, 

12 3 v 4- 12 2 

then 12 = 3 X 4, or — = —-— = 3, and — = 12 X 4 = 48. 

4 4 3 

Hence, (i)12 X 4 = (-J)^-. 

o 

In the act of discharging, the potential energy of the condenser or 
conductor decreases, while kinetic energy due to the current of dis¬ 
charge will be acquired. Hence, when potential energy has fallen to 
zero the current will still flow, due to its acquired kinetic energy. 
This will then charge the condenser oppositely and potential energy 





HERTZ EXPERIMENTS. 


ot 

/V 1 

is again acquired. Thus oscillations would be set up of prolonged 
duration, were there no resistance in the circuits; but as all circuits 
possess some resistance, heat will be generated in accordance with the 
c 2 r law, and obviously if the resistance be great the oscillations will 
quickly cease, or the potential energy may be dissipated in one quarter 
vibration. (See Appendix, p. 300.) 

Dr. Lodge has suggested the following as a perfect mechanical 
analogy to the charge, capacity, inductance, and resistance of a circuit, 
namely, a weighted spring bent back in a viscous medium. The 
bending or displacement of the spring corresponds to the charge; the 
tension or elasticity of the spring to capacity; the weight on the 
spring to inertia or inductance; and the friction of the viscous me¬ 
dium to resistance. 

The rate at which electric oscillations occur in a suitable con¬ 
denser or conductor may be many millions per second. According to 
the same authority, if an electrostatic charge on a metal sphere two 
feet in diameter be disturbed, the charge will oscillate at the rate of 
300,000,000 periods per second, and this will radiate into space-waves 
about three feet in length. The shortest “ ethereal” wave thus far 
produced by electromagnetic means is about .15 inch in length. This 
is still very much longer than the longest light-wave, and is sixty or 
seventy times longer than the longest dark heat-wave yet measured; 
the length of the heat-waves it is known falling between the light¬ 
waves and electromagnetic waves. 

In the electrical circuits employed in wireless telegraphy the re¬ 
sistance is small (if the spark-gap and filings-coherer are eliminated) 
and is commonly disregarded in computing the components of the 
circuit. In fact, as noted, if the resistance be too great the discharge 
will not be oscillatory. The time of a complete oscillation of a circuit 
containing inductance and capacity is expressed by the formula 
T — 2 n fo, where t is the time in seconds, tt is the ratio of cir¬ 
cumference to diameter, K is the capacity in farads, and l the induc¬ 
tance in henrys, or T _ 6,2832 Vkl. 

Hertz Experiments.— In proceeding with his experiments Hertz 
reasoned that as those waves which correspond to light affect the eye 
when they fall upon it, so should the electric waves of the ether affect 
a suitable electric “ eye,” or detector, when they fall upon it. The 
j^ppj^ratus employed by Hertz to show the existence of electric Tva\os 




22 


WIRELESS TELEGRAPHY. 



[ 


w 


b h w 





in free space consisted essentially of an electric oscillator and an 
electric resonator, or wave-detector. The oscillator is a device for set¬ 
ting up electric oscillations in a circuit, which in turn radiate or emit 
electric waves in free space. Such an oscillator and detector is out¬ 
lined in Fig. 9. The generator consists of the induction coil i, the 

terminals of the secondary wire being connected 
to small brass balls bb, to which short metal 
cylinders or wings w w are attached. The balls 
are separated by a short air-space or spark-gap 
s, across which sparks jump when the coil is in 
operation. At such times electric oscillations 
are set up in the oscillating circuit, the rate of 
which varies with the electrical dimensions of 
the circuit. The knobs and wings of the oscil¬ 
lator may be considered to correspond to the 
two widely separated plates of a condenser the 
dielectric of which is the air. The vibrations 
of the interrupter a set up pulsations of cur¬ 
rent in the primary circuit of the induction 
coil i, which by induction set up alternations of 
greatly enhanced electromotive force in the 
secondary coil, which in turn produce oscillations in the circuit b b w to, 
as stated, which circuit, it will be understood, is the oscillator proper. 

These oscillations are due to the fact that the discharge of the 
induction coil raises the discharge knobs b b to a very high poten¬ 
tial, this causing a disruptive spark across the air-space separating 
the knobs, which spark in turn reduces the resistance of the air to 
such an extent that oscillations are set up. Thus, as neatly stated 
by F. K. Vreeland: “ Suppose the air-gap to break down. A cur¬ 
rent surges across the gap, the stress in the dielectric is relieved, 
and displacement currents begin to flow back along the lines of 
force. It is well known that a variable current in a conductor 
induces similar currents in neighboring parallel conductors. So 
also in the dielectric: the displacement currents suddenly set up 
by the discharge of the oscillator induce similar displacement cur¬ 
rents in the adjoining portions of the dielectric, and so the dis¬ 
turbance is propagated outward from place to place in an ever- 
expanding wave. At the moment when the conductors or balls are 
completelv discharged and the current flowing across the spark-gap 


Fig. 9. Oscillator and 
Detector. 



















HERTZ DETECTOR. 


23 


is a maximum the energy of the oscillation is entirely kinetic, that is, 
magnetic, and no lines of force proceed from the oscillator. As the 
conductors become charged again with opposite polarities this changes 
into potential energy, stored in the strained dielectrics, about the 
oscillator. And these alternations of potential and kinetic energy are 
transmitted outward in somewhat the same way as sound is trans¬ 
mitted from a vibrating tuning-fork—here a layer of moving air under 
normal pressure, next a layer of compressed air without motion, and 
so on, only in the case of electric waves the direction of the current 
and of the stress which alternates with it is perpendicular (transverse) 
to the line of propagation, while in the case of sound the action is in 
the direction of propagation. Indeed, the action of the ether may 
be compared to the motion of a series of incompressible plates, capable 
of sliding over each other, but bound together by an elastic connec¬ 
tion which tends to make them slide back to the position of equilib¬ 
rium after being displaced. (See also pages 32, 33, 34.) 

The rate at which the armature or other circuit-breaker of an in¬ 
duction coil vibrates may vary from fifty, or less, to hundreds of vibra¬ 
tions per second. The oscillations of the electric oscillator may be 
many millions per second. Some of the early oscillators employed in 
wireless telegraphy had an oscillation period of about 250,000,000 per 
second; some of the latest, about 1,000,000 per second or less. It 
is evident, therefore, that the induction coil, or other alternating cur¬ 
rent generator, merely serves to strike the blow, so to speak, that sets 
up the rapid electric oscillations in the oscillating circuit, analogously 
as if we wish to keep a tuning-fork in vibration it must be struck or 
otherwise acted upon at intervals. 

It may be noted that the electromotive force at the terminals of 
the secondary wire of some of the induction coils used will reach 
200,000 volts. The current strength is, however, comparatively 
small. 

Hertz assumed that if the electric oscillations produced by the 
oscillator set up corresponding waves in the ether of free space, these 
waves should in turn set up electric oscillations in a suitable receiver, 
or “eye,” within the range of their influence. He therefore em¬ 
ployed as a detector of these waves a copper wire D (Fig. 9), of nearly 
circular shape, about sixteen inches in diameter, but broken at one 
point cl. On the end cl of this wire he placed small metal knobs, the 
distance between which could be accurately regulated by a mierom. 


24 


WIRELESS TELEGRAPHY'. 


•eter screw. This wire was upheld by an insulated support, a few 
feet from the oscillator. With the room darkened minute sparks were 
observed passing between the discharge-knobs d of the detector when 
the oscillator was in operation, and the results of this simple experiment 
have been generally accepted as proof of the existence of electric 
waves in free space. Hertz, however, did not rest with this demon¬ 
stration of the accuracy of Maxwell’s theory, but also in the course of 
his subsequent masterly experiments showed that, like sound, heat, and 
light waves, these electric waves could be reflected, refracted, concen¬ 
trated in parallel rays and to a focus, etc. 

The foregoing and many other tests, according to De Tunzelman, 
were made by Hertz without particular regard to having the second¬ 
ary circuit (that is, the detector or micrometer circuit) in strict syn- 
tonyor harmony with the primary or oscillator circuit. In order, 
therefore, De Tunzelman states in his detailed description of these 
tests, from which description these data are drawn (see Fleming’s 
“ Alternate Current Transformer”), to determine whether any change 
in the capacity or inductance of either of well-tuned circuits would be 
noticeable in the results, Dr. Hertz replaced the conductors w w 
(Fig. 9) by two straight wires each .19 inch diameter and 51 inches 
long. Two hollow spheres about 11.8 inch in diameter were ar¬ 
ranged to slide over these wires, one on each side of the discharge- 
gap, and as the spheres were movable on the wires the length of the 
conductors could be varied by moving them either way, since they 
virtually formed the terminals of the conductor, electrically con¬ 
sidered. The micrometer circuit was composed of a copper wire .078 
inch diameter, in the form of a square, the sides of which were each 
29.5 inches. This circuit was designed by Hertz to have a slightly 
shorter oscillatory period than the primary wires. One of the sides 
of the square was then placed within 11.8 inches of the primary wires 
and parallel thereto. When thus placed the sparking distance at the 
micrometer was .035 inch. Two metal spheres 3.14 inches in diame¬ 
ter were then placed in contact with the terminals of the micrometer 
circuit, which increased the sparking distance to .098 inch. Dr. 
Hertz found that the capacity of the micrometer circuit could be 
readily adjusted by the simple expedient of suspending from its ter¬ 
minals two parallel wires, the length and distance of which could be 
varied as desired. By this means he found that with a certain ad¬ 
justment the sparking distance at the micrometer knobs could be in- 


HERTZ DETECTOR. 


25 


creased up to .117 inch; but this was the maximum, any further 
lengthening or shortening of these wires reducing the sparking dis¬ 
tance. Further experiments were then made, including varying the 
capacity of the wires of the primary circuit to diminish its rate of 
oscillation, which experiments verified the results previously obtained, 
“and a series of experiments in which the length and capacities of the 
circuits were varied in different ways showed conclusively that the 
maximum effect does not depend on the conditions of either one of 
the circuits, but on the existence of the proper relation between them. 
The effect of varying the inductance of the circuit was also shown by 
experiment. This was done by varying the length of the rectangle, 
hut leaving its breadth constant. The length varied from about four 
inches to about eight feet. It was found that the maximum sparking 
effect was reached with a length of about six feet.” 

Dr. Hertz also showed in his further experiments that very rapid 
electric oscillations such as he was dealing with, of the order of 
100,000,000 per second, are confined to the outside portions, or 
“ skin,” of the conductors along which they are propagated, and that 
their propagation in a wire has a definite velocity independent of its 
dimensions and material, iron not being an exception. Also that the 
velocity of propagation of electric waves in air corresponded with the 
velocity of light, and this was afterward shown by Sarasin and De la 
Five to be true of the velocity of these rapid electric waves along wires. 

Hertz also showed that metals and other good conductors are 
opaque to and reflect electric waves. Further, that such conductors, 
when used as reflectors, to give best results, must be large relative 
to the length of the wave, and that the reflector must not be fur¬ 
ther than a quarter wave-length from the oscillator. These condi¬ 
tions have virtually prohibited the successful employment of reflect¬ 
ors to direct the waves in wireless telegraphy, although metallic 
reflectors have been tested for this purpose experimentally. Lodge 
has shown that such substances as the human body and a wet towel 
will also reflect the waves slightly, and that copper is a better reflector 
than lead in the ratio of 100 to 40. The fact that electric waves 
like light waves can be so reflected, and refracted, concentrated in 
parallel rays, etc., markedly differentiates electric radiation and elec¬ 
tromagnetic induction; with the latter these phenomena are not pro¬ 
ducible. (See p. 31.) (See reflectors, p. 129.) 




CHAPTER IV. 


EARLY EXPERIMENTS IN ELECTRIC WAVE TELEGRAPHY. 


BRANLY COHERER, LODGE EXPERIMENTS, ETC. 

By the Hertz detector the distance at which electric waves could 
be detected was very limited, perhaps ten or twelve feet at most, and 
hence it is not likely that much would have been done in the utiliza¬ 
tion of these waves for telegraphic purposes had progress rested there, 
but fortunately it did not. Shortly after the experiments of Hertz 
Dr. Branlv discovered that loose metal filings, which in a normal 
state have a high electrical resistance, lose this resistance in the 
presence of electric oscillations and become practically conductors of 
electricity. This Branly showed by placing metal filings in a glass 
box or tube ic, Fig. 10, and making them part of an ordinary electric 

circuit. According to the common 
explanation, when electric waves 
are set up in the neighborhood of 
this circuit, electromotive forces 
are generated in it which appear 
to bring the filings more closely 
together, that is, to cohere, and 
thus their electrical resistance 
decreases, from which cause this 
piece of apparatus was termed by Dr. 0. J. Lodge a coherer (although 
Dr. Branly himself termed it a radio-conductor). Hence the receiving 
instrument, G in the figure, which may be a telegraph relay, that nor¬ 
mally would not indicate any sign of current from the small battery b, 
will be operated when electric oscillations are set up. Prof. Branly 
further found that when the filings had once cohered they retained 
their low resistance until shaken apart, for instance, by tapping on the 
tube. In 1894 Lodge showed that the Branly coherer could bo em¬ 
ployed to transmit telegraphic signals, and in order that the filings 



Pig. 10. Branly Coherer. 





















LODGE APPARATUS. 


27 


should not remain “cohered ” after the cessation of the electric oscilla¬ 
tions, he devised an electro-mechanical “tapper” on the principle of 
the ordinary “ buzzer,” or electric door-bell, the hammer of which was 
caused to tap the glass tube as long as the electric oscillations continued. 
The filings thus virtually take the place of a key in the ordinary 
telegraph circuit. In the normal state the key is open; in the 
presence of electrical oscillations the key is closed. Thus, by opening 
and closing the key for a longer or shorter period, signals correspond¬ 
ing to dots and dashes may be produced. In other words, by setting 
up electric oscillations for periods of time corresponding to dots and 
dashes, messages may be transmitted from the sending station, and 
if, at the receiving station, a recording instrument (controlled by the 
coherer), such as the ordinary Morse register, be provided, a record 
of the message in dots and dashes may be obtained. Dr. Lodge (now 
Sir Oliver Lodge) in fact used a tapper operated continuously by 
clockwork. 



In 1895-96 Poppoff and others utilized the coherer to show the 
existence of atmospheric electricity, using for the purpose a vertical 
wire attached to the coherer. JLhe transmitter and lece.vei appaiatus 
of an experimental wireless telegraph outfit such as was used by Dr. 
Lodge in 1894 are outlined in Figs. 11 and 12. In Fig. 11 o is the 
oscillator apparatus, which comprises the primary wire and secondary 
wire of an ordinary induction coil i, the metal balls b b , and the metal 
“wings” ww. The terminals of the secondary wire of I are con- 

















































28 


WIRELESS TELEGRAPHY. 


nectecl as shown to V V and w w. The balls V V are about three fourths 
of an inch in diameter, and may be separated from one sixteenth to 
three fourths of an inch, depending on the strength of the coil, the 
capacity of the circuit, etc. The wings are brass or copper strips 
about one inch wide by twelve inches long. Ordinary No. 14 or 18 
copper wire will serve as wings for simple experimental purposes. 
For transmitting signals across a distance of fifty feet these wires need 
not be over three or four feet in length, using an induction coil giving 
a two-inch spark. Signals are sent by opening and closing key K in 
the primary wire of the coil. (See also description of Fig. 26.) 

In Fig. 12, which represents the Lodge receiving apparatus, k is a 
coherer; t is the Lodge tapper and call-bell combined; r is a sensi¬ 
tive Morse relay. Wires w w' are extended from the ends of the 
coherer analogously as in the case of the oscillator. T his coherer 
consists of a glass tube about four inches in length, with small metal 
rods 11\ of suitable size to snugly fit the bore of the tube, and are 

inserted at each end as indicated. These rods come nearly to the 

middle of the tube, but do not touch, leaving a small space in which 
the filings f are placed. The filings may be of nickel. The rods in 
this case may be provided with adjusting-screws s s' to regulate the 
distance between their ends in the tube. 

A few words of description of the operation of the receiving 
apparatus will here suffice. Normally the armature-lever l' of the 
tapper is given a tension which holds it against the contact c. Nor¬ 
mally also the armature-lever l of relay R is on its back or insulated 
stop x. Hence, at this time, the local circuit of battery V is open. 
When the filings cohere, relay R is magnetized by one dry cell b and 

its lever l moves over to contact c', closing circuit of battery b', when 

the electromagnet of T attracts its armature, which opens the circuit 
of V at contact c. At once the armature of T flies hack on its contact 
point, at the same time striking the tube, decohering the filings, and 
demagnetizing relay R, whose armature-lever l is brought to its back 
contact x by a retractile spring not shown in the figure. Immediately, 
however, the filings again cohere (assuming that the oscillations con¬ 
tinue), with the result that R is magnetized, again closing circuit of 
V at c', whereby T is again magnetized, and the actions just described 
are repeated many times in a second. 


CHAPTER Y. 


THEORIES OF ELECTRIC-WAVE PROPAGATION—THE ELEC¬ 
TRONIC THEORY. 

THEORIES OF ELECTRIC-WAVE PROPAGATION. 

Beginning his experiments in Italy in 1895, with vertical wires 
twenty feet high, Marconi found that he could get signals at a dis¬ 
tance of one mile, and that by doubling the height of the vertical wire 
at both stations, signals could be transmitted to four times that dis¬ 
tance. Thus, with wires forty feet high he could signal four miles, 
and with wires eighty feet high, sixteen miles, and he thought the 
signaling distance would follow this rule, hut subsequent experiments 
liave shown that it requires some modification; and as a result of 
experiments by Captain Bonomo, of the Italian navy, it has been 
found that for the usual Marconi ship apparatus the signaling distance 
appears to vary according to the formula, A — 0.15 VD, where L is 
the length of the vertical wire, and D is distance, in meters, and 0.15 
is a constant. Subsequently, Marconi has employed in his transat¬ 
lantic experiments many parallel wires, frequently termed antennae, 
over two hundred feet high, and has succeeded in transmitting sig¬ 
nals to a distance exceeding two thousand miles. 

The amount of electrical energy employed in setting up the elec¬ 
tric oscillations for a distance of about 20 miles is approximately 
150 watts, furnished by five storage cells, at a pressure of about 10 
volts and 15 amperes, giving about one fifth of a horse-power. These 
-cells are frequently charged by a large number of dry cells in mul¬ 
tiple. An ordinary telegraph relay may be operated at a distance of 
200 miles at an expenditure of about 3 watts at the transmitting end 
of a telegraph wire, or with one fiftieth of the energy used in operating 
the electrical oscillator in question. The actual electrical energy 
required to operate the telegraph relay is about .21 watt, the rest of 
the energy being consumed in the lino wire itself. It must not, how- 


30 


WIRELESS TELEGRAPHY. 


ever, be assumed from this that the coherer is a less sensitive electrical 
receiver than the Morse telegraph relay; nor will it be, when it is 
reflected that the electrical energy expended in the case of the relay 
is, so to speak, mainly confined to the wire, as, analogously, sound¬ 
waves are confined within a speaking-tube, whereas the electrical energy 
of the oscillator is radiated into space in every direction, and thus but 
a small portion of the total energy reaches the receiving vertical wire. 
It may readily be calculated that the electrical energy received on a 
surface one foot square at a distance of but one mile from the trans¬ 
mitter is less than the one three-hundred-and-fifty-millionth of the 
total energy radiated, and, it may be further noted, the energy actually 
radiated as electric waves is perhaps not more than six or eight one- 
hundredths of the energy developed at the oscillator, the remainder 
being lost in the induction coil as heat, etc., and at the spark-gap as 
heat, light, and sound. The foregoing with relation to the proportion 
of energy reaching the receiving wire and the amount of the energy 
radiated is based on the assumption that the waves are actually radi¬ 
ated in every direction in space, and that the rate at which the energy 
is radiated corresponds to the input at the oscillator, minus the losses. 
If it should develop that the atmosphere, earth, or ocean plays a part 
in guiding or conducting the waves, and that the energy thrown into 
the vertical wire is radiated at a greater rate than it is received (a view 
that was suggested by Mr. Edison in a conversation on this subject 
with the author several years ago), the view implied as to the super¬ 
sensitiveness of the receiver must be qualified.* 

It was at first thought that signaling by wireless telegraphy would 
be limited by the curvature of the earth to comparatively short dis¬ 
tances, inasmuch as it is not practicable to secure masts or other suit¬ 
able supports for the vertical wires high enough to surmount the 
earth’s convex surface between points several hundred miles apart, 
and it was assumed that the earth would prove to be a barrier to 
electric waves traveling in straight lines, like luminous waves, which, 
it is known, are obstructed by substances opaque to light—that is, 
to substances which are opaque to ether-waves of the length of light¬ 
waves. From the more recent long-distance experiments with wire¬ 
less telegraphy, however, it would appear that given a sufficiently 

* According to tests by Dr. De Forest, with a one-kilowatt transmitter, a hot-wire ammeter will 
indicate a current of three or more amperes in the vertical wire, with an E. M. F. of 20,000 volts at 
the oscillator, which gives, roughly, a calculated momentary rate of radiation of about 70 kilowatts: 
explainable, he notes, by Hert’z calculations of rate of energy radiated from a dumb-bell oscillator. 


THE ETHER. 


31 


powerful transmitter and a sufficiently sensitive receiver, it is possible, 
as just intimated, to detect signals at a distance measured at least by 
the width of the Atlantic Ocean, and that with vertical wires not 
much exceeding two hundred feet in height. 

A number of theories have been advanced to explain the fact that 
signals are thus received at distances much beyond what would be 
possible did the earth intercept the electric waves traveling in straight 
lines. Before enumerating some of these theories it may be premised 
that inasmuch as the mechanism of the ether is not yet understood, 
it is evident that attempts at explanations of the phenomena accom¬ 
panying disturbances of or in that medium must at best be more or 
less hypothetical. At present we are, it may be admitted, with regard 
to our knowledge of the ether in somewhat the position of the ancients 
relative to their knowledge of the wind: we hear, so to speak, the 
sound of the ether, but we know not whence it cometh or whither 
it goeth. We can by suitable devices set up disturbances in the 
ether, analogously as we can set up disturbances in the air, but we 
are as yet ignorant of the action of the ether when so disturbed, and 
know nothing definitely of its constituents. 

Among the theories relative to the manner in which the electric 
waves of wireless telegraphy are propagated are those in which it is 
assumed that the waves are diffracted or reflected around the natural 
curvature of the earth. Other theories are that the waves are propa¬ 
gated by electrostatic or electromagnetic induction; by oscillatory 
currents in the earth; by reflection between the upper atmosphere 
and the ocean; by disturbing the equilibrium of the earth’s charge, 
known facetiously as “ wobbling ” the earth’s charge; by bringing the 
vertical wire into resonance with the earth’s capacity; and by slidiug 
or gliding waves or half-waves over the surface of the earth and ocean. 

As noted by Mr. J. E. Taylor in a very interesting article on elec¬ 
tric radiation (“London Electrical Review,” May 12, 19, 1899), the 
electrostatic and electromagnetic theories are hardly tenable, for the 
reason that electromagnetic induction effects decrease at least as the 
inverse cube of the distance, which, for long distances, would diminish 
the force so rapidly the effect would not be perceptible. An essen- 
sential difference between electromagnetic induction and electromag¬ 
netic radiation is that the field of force of induction being, as it is 
termed, a volume effect, expands as a whole from the source, and is 
under the control of the source, increasing, decreasing, and dying out 


32 


WIRELESS TELEGRAPHY. 


with the source; whereas electromagnetic radiation, consisting of 
electric waves in free space, and assuming that it corresponds to- 
luminous radiation, is independent of the source once it has been 
detached therefrom, and goes on traveling outward indefinitely, if it 
meets no obstacles, as an ever-expanding, self-closed line of force. It 
is necessary, as Taylor also observes, in order that an electric field 
may exist independent of any conductors, that the lines of electric 
force shall be self-closed. Such lines of strain are generally sup¬ 
posed to exist with both ends terminated on conductors, whereas in 
fact they can be cut up or subdivided and joined again, stretched 
out like elastic threads or allowed to contract and shorten themselves: 
indefinitely. 

Prior to making further reference to other theories of electric- 
wave propagation, the supposed action that takes place in and around 
the Hertz oscillator in the production and propagation of free electric 
waves in space, as expounded by Maxwell, Hertz, Heaviside, Poyn- 
ting, J. J. Thomson, and others, may first be considered. 

The Hertz oscillator, as stated elsewhere, corresponds to a con¬ 
denser with widely separated plates. In Fig. 13, a a are rods of the 
Hertz oscillator, with the spark-balls b, placed vertically. In the act 
of charging the rods a a; so-called lines of electric force or strain s s 
spring out from the rods, not only in one section of the rods as 
indicated in the figure, but all around them, with the rods as a center. 
According to Maxwell's theory of displacement currents in dielectrics, 
when the circuit of a condenser is closed, in the ordinary sense, a 
current continues to flow in the circuit (considering the dielectric part 
of the circuit), but the dielectric, acting as though it were composed 
of innumerable small elastic rods, at once sets up an opposing force, 
which increases the more the rods are bent back, so to speak, until 
their opposing force equals the charging force, when the displacement 
current ceases to flow. At this time the condenser has acquired the 
potential of the charging E. M. F. When the electric pressure of 
the external E. M. F. breaks down the resistance at the spark-gap 
the potential energy stored in the dielectric is returned to the circuit 
and a current flows across the gap. The strain in the dielectric is 
thereby relieved, concurrently with which, according to Poynting, 
the ends of the positive lines of electric strain contract and run or 
slide down the rod, and the ends of the negative lines move up, as 
indicated in Fig. 14. The extreme outside portions of the lines of 


THEORY OF HERTZ OSCILLATOR. 33 

strain also tend to contract, but as such portions of the lines move 
more slowly than the ends of the lines on the conductor, these ends 
meet, and as they cannot pass one another the respective ends are 
detached—snapped or whipped oft—from the conductor, and, uniting, 
form closed electric lines of force, which are radiated into space as 



Fig. 13. 




Fig. 15. 


outlined in Fig. 15; the detached circles or lines of strain being 
shoved away, as it were, from the conductor by the succeeding de¬ 
tached circles. (This action has been variously likened to the action 
by which rings of smoke are shot out from a locomotive’s smoke-stack, 
soap-bubbles snapped off from a pipe, etc.) Coincidentally also with 
and due to the collapse of the electric lines of strain, magnetic lines 
or circles of force are set up concentric with the rods a «, and at right 
angles to the electric lines of strain, as indicated by the transverse 
lines in Fig. 15. When the magnetic lines of strain are at a maximum, 
namely, at the end of a quarter-period (p. 20), the electric lines of 
strain, that is, the potential energy, will have disappeared. At once, 
however, the magnetic lines of force begin to collapse, thereby again 
setting up electric lines of strain (potential energy) in the dielectric 
as before, but in the opposite direction, so that the upper end of the 
rod in Fig. 13 will now be charged with negative and the lower with 
positive potential. Hence, at the next collapse of the electric lines 
of strain the magnetic lines of force will be of opposite sign to the 
preceding lines of magnetic force, as will also be the radiated or 
detached closed lines of electric and magnetic force, as indicated by the 
arrow-heads in Fig. 15. These processes are repeated until the energy 
of the system is exhausted, and the oscillations cease, to be renewed 
when the rods are again charged and the spark-gap breaks down. 

The detached lines of electric and magnetic force thus jointly con¬ 
stitute electric radiation or free electric waves, which are propagated 













34 


WIRELESS TELEGRAPHY. 


in the ether as ever-expanding electromagnetic waves or undulations, 
which become more spherical as they proceed from their source. These 
are Hertzian or free waves in the strict sense, but Hertz also showed, 
in the course of the experiments referred to (p. 24), that these waves 
are guided or conducted, at the speed of light, by wires or conduc¬ 
tors upon which they may converge, and that when conductors are 
led from the vicinity of the oscillator the waves may be detected at a 
greater distance than when such conductors are not present. 

The reflection and diffraction theories assume that Hertz waves 
are propagated outward from the transmitter as light is propagated 
from its source in straight lines, and when the waves come to an 
obstacle, such as the curvature of the earth, they are reflected or 
diffracted around or past it. Since the days of Newton the charac¬ 
teristic colors of the sky have been attributed to the reflection of light¬ 
waves by particles of matter in the atmosphere, large by comparison 
with the length of the light-waves. Hence the reflection theory is 
objected to on the ground that particles large by comparison with the 
waves employed in wireless telegraphy do not exist in the atmosphere. 
The diffraction theory is not regarded as available, for the reason that 
it has been shown that diffraction phenomena on a suitably large scale 
are only obtainable when the thickness of the diffracting edge is at all 
comparable with the length of the wave, a requirement which is not 
supplied by the curved surface of the earth. (See p. 38.) The 
theory of a zigzag onward reflection of the waves between the surface 
of the ocean and the upper atmosphere is also by some considered 
unsound because of the assumed rapid diminution of intensity of 
the waves that this would involve. 

It has also been suggested that the waves are propagated in straight 
lines from the vertical wire, and when they reach the convex surface 
of the sea pass through it as if it were a dielectric, but it has been 
pointed out that sea-water, as a conductor, is opaque to and reflects waves 
of the frequency used in wireless telegraphy. (See pp. 25, 292, 299.) 

The fact that so much better results are obtained in electric-wave 
signaling when the vertical wire is grounded than when it is insulated 
from the earth, indicated that the earth must play an important part 
in the propagation of the waves, and this, with other reasons, has led 
to the supposition that the surface of the earth or sea, especially the 
latter, acts as a guide or conductor on which the waves converge (as 
in the Hertz experiments with conductors), the conductor holding the 


IMAGE THEORY. 


35 


waves, as it were, to a given course and preventing them from spread¬ 
ing out into free space. On this general view the waves are supposed 
to slide or glide over the surface of the earth or sea, hence this is 
termed the sliding-wave theory. As this theory appears to best explain 
the phenomena met with in the operation of wireless telegraphy, it 
has been in one form or another favorably received by some of the 
workers in this field. 

The sliding-wave theory in its entirety was perhaps first proposed 
by Mr. Taylor in the article mentioned. The explanation of this 
theory may be aided by means of the accompanying diagrams. It is 
here assumed that the grounded vertical wire is equal to one half of 
a Hertz oscillator, the other half being the earth itself directly below 
the vertical wire. On this assumption the earth is a perfect conduc¬ 
tor. Hence the vertical wire may be supposed to have a reflected 
counterpart directly below it, such as would be seen under a pencil 
standing vertically on the surface of a mirror lying horizontally on a 
table. This is in accordance with what is termed the image theory, 
first advanced by Helaricci and Blondel. Stated briefly in another 
way, such a vertical wire is a Hertz oscillator divided in the middle 
by a reflecting conducting surface. Inasmuch as this center is a 
point of zero potential, the conducting surface has no effect upon the 
oscillations except that it theoretically divides them into two half-sys¬ 
tems of oscillations, either of which may be removed without affect¬ 
ing the other. Hence the grounded vertical wire with the conduct¬ 
ing surface of the earth will have a real oscillatory system above the 
earth and an imaginary one below the conducting surface, as indi¬ 
cated by the dotted lines, Fig. 16. The oscillations occurring in this 
system may then correspond to those in the Hertz oscillator, a com¬ 
plete period of oscillations consisting of a wave from the spark- 
gap to the top of the antennae, back to the spark-gap, thence to the 
foot of the reflected or imaginary wire and back to the spark-gap, 
which constitutes a wave-length four times that of the vertical wire 
proper. (As intimated elsewhere, this quarter-length may be increased 
by adding capacity or inductance to the antenna, inasmuch as wave¬ 
length X = %7T 4/ k l x velocity per second.) (See p. 21.) 

Referring to Fig. 16, it is assumed, as in the case of the Hertz 
oscillator, that when the vertical wire A is charged, electric lines of 
force are set up in the dielectric, the air, one foot of which lines rests 
on the ground, the other on the vertical wire as indicated. 



36 


WIRELESS TELEGRAPHY. 


In many of Lodge’s early experiments and lectures he showed 
results corresponding to those obtained by the Lecher system of wires- 
(Figs. 87 and 88). In these experiments the source of the oscillating 
currents were Leyden jars connected in series. The wires were con¬ 
tinued a long distance from the oscillator, and it was shown that the 
waves follow the wires around loops, curves, etc. Taylor, in pro¬ 
pounding his theory, says if these wires or one of them is put to* 
earth instead of being insulated, the waves will pass on and skim or 
glide over the surface of the earth indefinitely. If one jar and one- 
wire only are used, waves will still be propagated. This arrangement 
may then be considered to correspond to the grounded vertical-wire 
system. The vertical wire is one coating of the jar, the earth’s sur¬ 
face at the base of the wire is the other coating, and the earth itself 




Fig. 16. Fig. 17. 

takes the place of the attached Lodge or Lecher wire. When the dis¬ 
charge occurs the upper ends of the lines glide down the wire in the 
manner described in connection with the Hertz oscillator, to the earth, 
forming waves similar to those which propagate themselves along 
wires. In this case the detached waves travel out radially in the 
shape of huge concentric circles, not into space, but sliding over the 
surface of the ground as indicated in Fig. 17. The magnetic field 
which accompanies the moving field of electric strain is in the shape 
of concentric circles (indicated by the transverse lines), which circles 
are of small density, owing to their large circumference. According 
to Poynting, the absorption of energy is proportional to the density 
of the magnetic field and also to the resistance of the earth. Con¬ 
sequently, in this case but little energy is absorbed, and it is still 
less as the conductivity of the sliding surface is increased, which, 
Taylor adds, doubtless explains the fact that better results are obtained 
over sea than over land. Further, this theory also explains why hills 
and the curvature of the earth are not obstacles to the propagation of 












SLIDING-WAVE THEORY. 


37 

these waves, for on this theory the waves travel over or around such 
surfaces analogously as they travel over the bent or looped wire in 
Lodge’s experiments. Since also with this form of wave sliding off 
from the grounded vertical wire there is no reflection from the earth 
into space and no radiation into space, as would he the case with ver¬ 
tical conductors without the ground connection or its equivalent, 
Mr. Taylor assumes that the intensity of the waves should not be 
much less than inversely as the distance from the source, and com¬ 
bining this with the increase of height of the vertical wire, the result 
of the variation of distance with the square of the length of the wire 
is obtained. According to Professor Blondel, the intensity dimin¬ 
ishes inversely as the square of the distance. 

Professor Fessenden, in a paper read before the American Insti¬ 
tute of Electrical Engineers, November 22, 1899, discussed a sliding- 
wave theory on which it is assumed that the waves emitted from the 
vertical wire are propagated as sliding half-waves or loops over the sur¬ 
face of the sea or earth. As these waves proceed from the transmitter 
they expand, but their sides draw closer and closer together until they 
are nearly parallel. In tests made by Professor Fessenden in which 
the hot-wire barretter was used as a quantitative receiving instrument, 
it was ascertained that after the first few wave-lengths the intensity 
of the waves diminishes as the square of the distance, and that the 
height of the waves increases directly as the distance. The tests were 
made as follows:* The transmitting apparatus was placed on a boat on 
one side of an island, while the receiving apparatus, including a ver¬ 
tical wire in each *case, was set up on the other side of the island on 
a wharf extending out over the water a distance of about three hun¬ 
dred feet. The apparatus employed in making these tests included 
three separate devices to detect the intensity of the waves at various 
distances, the height of the waves, and the presence of waves in the 
earth or water, namely: a detector in circuit with a vertical wire which 
was moved sideways; a detector in circuit with a bundle of fine iron 
wire around which were a few turns of copper wire moved vertically; 
and two large copper triangles placed apex to apex with their bases 
resting on the earth and with a detector between the apexes of the 
triangles. The tests demonstrated also that no currents are gener¬ 
ated in the water or earth in the direction of propagation of the waves 
while the direction is unchanged, but that currents are generated 

* See article by A. F. Colling, “ Electrical World and Engineer," September 19, 1903. 


38 


WIRELESS TELEGRAPHY. 


when the direction of propagation is changed. The bank of the 
island was fifty feet high, and at the foot and top of the bank currents 
were detected which disappeared midway between the bottom and top 
of the bank, and at other level portions of the route. The tests also 
showed that at curvatures of the surface the intensity was greatest 
near the earth, this disproving the diffraction theory. 

In this relation Professor Fessenden points out the advantages of 
the hot-wire barretter, namely, its great sensitiveness (page 158), its 
practical freedom from hysteresis, inductance and capacity, and the 
fact that it gives the cumulative effect of the received energy, besides 
possessing the quality that the relation between the energy absorbed 
and increase of resistance is a straight line up to the point of melting. 

Another theory of electric-wave propagation, advanced by Sir 
0. Lodge, is that the transmitting and receiving vertical wires are 
plates of a huge condenser. Only one of the plates is charged during 
a sending operation, the other plate is at zero potential. He assumes 
that some trace of the electrostatic lines from the transmitter may 
extend to the elevated receiving wire. With the snap of the spark- 
gap and sudden discharge there is a cutting of the receiving wire by 
the electrostatic lines, with the resulting effect upon the detector. 

Professor Fleming advances another theory, in which he assumes 
that there is a propagation of electric action through the earth, which 
action may consist in a motion or atomic exchange of electrons, to¬ 
gether with the actions constituting a free electromagnetic wave in 
the ether above the earth. Each change or movement of a semi-loop 
of electric strain above ground, he further assumes, is accompanied 
by an equivalent action below ground in movements of the electrons 
on which the ends of the semi-loops of electric strain terminate. The 
office of the receiving vertical wire is to bring about a union between 
the two operations above and below ground. He, like Lodge, then 
likens the transmitting and receiving vertical wires and the earth to 
a large Hertz oscillator. Electric oscillations of a certain period are 
set-up by the discharge of a condenser in one part of the system and 
are propagated to the other part. In the earth there is a propaga¬ 
tion of electric oscillations; in the space above and between the ver¬ 
tical wires there is a propagation of electric waves. For other theories 
hereupon see Appendix, page 301. 


THE ELECTRONIC THEORY. 


39 


THE ELECTRONIC THEORY. 

From time immemorial it has been generally assumed that the atom 
of matter is indivisible—a body, as Clerk-Maxwell tersely puts it, that 
cannot be cut in two; but within a comparatively short time a new 
theory, termed the electric theory of matter, or the electronic theory, 
has been evolved, according to which the material atom, instead of 
being indivisible, is made up of positively and negatively charged 
electric units, or corpuscles, termed electrons. It may not be amiss 
to somewhat briefly review here the salient features of the theory as 
elucidated by the most active investigators of the phenomena con¬ 
cerned in the subject. One view is that the electron is a material 
corpuscle that has been detached or chipped in some way from an 
atom. Each chip so detached is an electron, a piece of detached mat¬ 
ter carrying a negative charge of electricity. The part of matter 
which remains contains the positive electron, which has not yet been 
discovered free or isolated. In combination the negative and positive 
electrons form a neutral substance, namely, the chemical atom. A 
modification of this view is that the electron is the isolated charge 
of electricity itself, and that all matter consists of an equal number of 
positive and negative electrons interlaced or inter-revolving in the 
atom, electricity thus being the fundamental part of all matter. It has 
been pointed out, however, that if the atom were composed of equal 
numbers of positive and negative electrons they would neutralize one 
another and would have no mass, therefore no inertia. Other investi¬ 
gators contend that these “chips” or electrons are from the hydrogen 
atom, and M. Villard has shown that the electrons have the same 
spectroscopic lines as hydrogen, and if all trace of hydrogen is removed 
the cathode rays (mentioned subsequently) are suppressed. 

It is assumed that the electrons of an atom are in stable orbital 
rotation around one another, that they possess inertia, are mutually 
attracted and repelled, and, in short, that each atom is a miniature 
solar system, in which the orbits of the various parts are calculated 
to be relatively as great as are those of the planets of that system. 
Since the electrons are assumed to possess the property of inertia, and 
inasmuch as the material atoms are by this theory aggregations of 
electrons, it is suggested that mechanical inertia may be explainable 
on the basis of electrical inertia or inductance. 

Again, it is assumed by other workers that the material atoms are 


40 


WIRELESS TELEGRAPHY. 


made up of concentric layers of positive and negative electrons, with 
always a layer of negative electrons outside. To account for the stable 
formation of the elements it is postulated that at distances almost 
infinitely small all electrons repel one another, regardless of whether 
positive or negative, while at other distances similar electrons repel 
and dissimilar electrons attract one another. To explain gravitation 
by this theory it is assumed either that all electrons attract one another 
when gathered together in atoms, or that the attractive force of dis¬ 
similar electrons is greater than the repelling force of similar elec¬ 
trons. It is further supposed that the number and arrangement of 
the positively and negatively charged electrons of an atom are dif¬ 
ferent for each element, but that in every case, starting from the 
smallest known atom, hydrogen, which was by many supposed to be 
the ultimate particle of all matter, the number of electrons in an atom 
is some multiple or sub-multiple of a smaller atom. For example, in 
the hydrogen atom there are, according to Dr. J. J. Thomson, the 
well-known authority on this subject, and other workers, 700 elec¬ 
trons; in the oxygen atom there are 16 times as many, or 11,200; in 
the sodium atom about 15,000; in the gold atom, 137,200; in the 
mercury atom, 140,000; and in the radium atom, 160,000 such elec¬ 
trons. It is thus apparently by the number of electrons in an atom, 
and by the particular manner in which they are arranged in the atom, 
that one atom is recognizable from another; analogously, perhaps, as 
different chemical combinations of molecules form different sub¬ 
stances. It would seem that the possible stable combinations or 
groupings and the number of such units in atoms would be limitless, 
and therefore that the number of different elements would be limit¬ 
less; but thus far such stable or seemingly stable combinations appear 
to be restricted to those of the known elements. It has, however, 
recently been suggested as within the possibilities that further inves¬ 
tigations with radium may lead to the discovery of an entire series of 
new elements. 

To fix an idea of the exceeding smallness of the electron, Sir O. 
Lodge has calculated that if the electron be considered as equal to 
the period at the end of a sentence, the atom of hydrogen would be 
relatively equal in size to a building 160 feet long, 80 feet broad, and 
40 feet high. The diameter of the mercury atom is taken to be the 
one one-hundred-millionth of a meter, and, using an analogy due to 
Lodge, the 140,000 electrons composing this atom occupy this space 


INERTIA OF ELECTRON. 


41 


as a few scattered soldiers might occupy a country, not by bodily 
bulk but by forceful activity. The same authority, noting that the 
mass or inertia of an electric charge depends on two factors, quantity 
and potential, observes that with a given charge on a sufficiently small 
sphere the potential can be raised to any desired value; thus any 
required inertia can be obtained. Therefore, to account for the inertia 
of the electron, its diameter must be one ten-million-millionth meter, 
lie also notes that the path open to a free electron in a body with the 
density of platinum is the one-millionth of a meter. Further, if the 
140,000 electrons composing a mercury atom be arranged in rows of 
50 across the diameter of the atom, the space left unoccupied by the 
electrons within the sphere is ten thousand million times the filled 
space. Hence the electrons may move comparatively unobstructedly 
in their orbits, but where collisions do occur it is assumed that they 
rarely collide directly. Dr. Thomson notes that a collision may be 
considered as occurring when an electron approaches so near a charged 
body that its direction of motion is appreciably changed. 

According to the theory of the ether developed by Dr. J. Lar- 
mor, to whom is due the idea of the orbital rotation of the electrons 
in an atom, the ether possesses a rotational elasticity, but its various 
parts resist entire rotation round an axis, yet may be sheared or dis¬ 
placed over one another (page 23). The strain by which the dis¬ 
placement is brought about is due to an electric force, and the strain 
disappears when the electric force is withdrawn. In this ether the 
electron is the center of an enduring strain point which can be moved 
about in the ether as a kink can be moved about in a rope, but not 
set free. The electrons only can set up disturbances in the ether 
and the ether only can move them, as though each had a “grip” of 
the other. 

That which has hitherto been considered as merely a charge of 
positive or negative electricity in a substance is by the electronic 
theory held to be due to an excess of free negative or a defect of posi¬ 
tive electrons; in other words, a negative charge is due to an excess 
of negative electrons, and a positive charge is due to the removal of a 
negative electron from the atom, which latter thereupon becomes 
positive—a theory which to this extent conforms to Franklin’s fluid 
theory, the difference being that what he termed negative electricity 
is known to be positive electricity, and vice versa. To account for 
.the phenomena of current electricity, etc., by the electronic theory, 


42 


WIRELESS TELEGRAPHY. 


it is supposed that in addition to the neutral electrons composing the 
atoms there are many so-called free electrons intermingling and inter¬ 
changing with the electrons of the atoms, and which, under the influ¬ 
ence of an electric force, are capable of moving comparatively freely 
through metals or other good conductors; whereas the structure of 
non-conductors is such that the electrons cannot move freely through 
them. In this relation it may be noted that nearly all good con¬ 
ductors of electricity are composed of single elements, while dielectrics 
or insulators, such as air, glass, ebonite, mica, and gutta-percha, are 
compound, or combinations of elements. Assuming that an action is 
constantly taking place in which the atoms of metals are split up into 
negatively and positively charged corpuscles, which again recombine 
to form neutral atoms, Dr. J. J. Thomson notes that in the normal 
state the number of such corpuscles that recombine in the neutral 
atom will equal those that have been set free. Consequently, swarms 
of these corpuscles, moving in all directions, gain or lose energy by 
colliding with the atoms of the metal, and acquire an average velocity 
of about 10,000,000 centimeters. This swarm of electrons under an 
electric force will be sent drifting along in a direction opposite to the 
electric force, this constituting, as just intimated, the electric current. 
Assuming, further, that these electrons are moving in a metal at the 
stated average velocity, it might be expected, Dr. Thomson adds, that 
some of them would escape into the surrounding air; but to do so, he 
points out that the electrons would require to possess a certain defi¬ 
nite amount of energy, for they are attracted by the positive electrons, 
and probably by the neutral atoms as well, which suffices to keep 
them within the metal. The electrons are known, however, to escape 
from or to be projected from an incandescent wire, from a cold metal 
when exposed to ultra-violet rays, from the cathode of a Crookes 
tube, and, as will be noted elsewhere, from radium. The same 
authority offers the following explanation why the electrical conduc¬ 
tivity of metals increases with a decrease of temperature. He notes 
that the amount of current carried across unit area is determined, 
first, by the number of free electrons per unit volume of the metal, 
and, second, by the freedom with which these electrons can move, 
under the electric force, between the atoms of the metal. The free¬ 
dom with which the electrons move depends upon the average velocity 
of the electrons, since if they are moving with very great velocity they 
cannot move far before they come into collision with an atom of the 


ELECTRICAL ATOMS. 


43 


metal, and thus the effect produced by the electric force is neutralized. 
The average velocity of the electron increases with the temperature, 
hence electric conductivity decreases with increased temperature. 

By the electronic theory an alternating current is due to a to-and- 
fro motion or vibration of electrons under the influence of a compara¬ 
tively slow alternating electric force, while a very rapid oscillation of 
the electrons in a conductor sets up, by reason of their intimate con¬ 
nection with the ether, a disturbance in the latter in the form of the 
so-called electric waves. It may be noted that although the electrons 
under the influence of the rapidly oscillating electric force vibrate 
at a very rapid rate, it does not follow that they traverse a large por¬ 
tion of the metal; their motion may be transmitted from particle to 
particle, analogously as air-particles propagate sound. In the latter 
case the total distance traveled by an air-particle may not be more 
than the one-millionth of an inch. 

The electric theory of matter, although of comparatively recent 
origin in a number of its features, is not, however, altogether one of 
a day, nor is it the conception of one mind or of the researches of 
one man. Thus, as regards the view that the atom is not an indi¬ 
visible particle of matter, many scientists have for years held that all 
the elements are modifications of a single hypothetical substance, pro- 
tyle, “the undifferentiated material of the universe.” Nor is the theory 
entirely new in its assumption that all matter is electrical. Faraday, 
Weber, Helmholtz, Clifford, and others had glimpses of this view; and 
the experimental work of Zeeman, Goldstein, Crookes, J. J. Thom¬ 
son, and others has greatly advanced the theory. Over thirty-five 
years ago Weber predicted that electrical phenomena were due to the 
existence of electrical atoms, the influence of which on one another 
depended on their position and relative accelerations and velocities^ 
Helmholtz and others also contended that the existence of electrical 
atoms followed from Faraday's laws of electrolysis, and Johnstone 
Stoney, to whom is due the term “electron,” showed that each chemical 
ion of the decomposed electrolyte carries a definite and constant quan¬ 
tity of electricity; and, since these charged ions are separated on the 
electrodes as neutral substances, there is an instant, however brief, 
when the charges must be capable of existing separately as elec¬ 
trical atoms. Clifford, in 1887, wrote, “There is great reason to 
believe that every material atom carries upon it a small electric cur¬ 
rent, if it does not wholly consist of this current.” 


-44 


WIRELESS TELEGRAPHY. 


The investigation of cathode rays, which rays are established by 
the discharge of a powerful induction coil through an air-exhausted, 
glass tube, also pointed to the probability of an electrical atom, for it 
was found that these rays, projected from the cathode (that is, the 
negative pole of the apparatus) in straight lines, like a shot from a 
gun, are deflected by a magnet, the direction in which the rays are 
deflected by the magnet proving that they are negatively charged. 
Dr. Thomson, it may be remarked, also succeeded in deflecting these 
rays by an electric charge, after some difficulty, occasioned by the fact 
that moving electrons electrify the gas through which they are pass¬ 
ing- and thus screen themselves from the effect of an external electric 
< force; but by reducing the pressure of the gas to a low point he suc¬ 
ceeded in deflecting the rays as stated. 

Cathode rays are now known to be electrons, that is, minute nega¬ 
tively charged particles moving at a speed variously estimated at one 
fifth, one third, or one half the speed of light, and which particles, 
prior to issuing from the conductor or cathode, must have existed in 
the conductor as an electric current, this giving strength to the sup¬ 
position that an electric current consists of the movement of free 
electrons in a conductor. On the other hand, Roentgen rays, which 
are part of the observed phenomena accompanying the cathode rays, 
are not deflected by a magnet, and hence are not regarded as charged 
particles, but rather as electric disturbances or “ splashes ” in the 
ether, due to the suddenly arrested motion of rapidly moving elec¬ 
trons by their impact with fixed groups of electrons—in other words, 
with a solid substance as we know it. Lodge has stated that the 
energy expended in stopping an electron within the thickness of a 
molecule, and when moving at a speed of about G200 miles per second, 
is about 10 watts (the minute time of stopping being the one-lnmdred- 
thousand-million-millionth of a second); but only a small fraction of 
this power goes out as electric radiation, namely, an amount equal to 
100 ergs, the rest of the energy taking the form of heat. In order, 
he adds, that all the energy may be radiated it would be necessary to 
stop the electron in something like the one-tenth of its own diameter. 

The investigations of Dr. Thomson have also shown that the 
charge on the negative electron is equal to that on the atom of hydro¬ 
gen in electrolysis, but that the mass of the electron is only one-thou¬ 
sandth that of the hydrogen atom. Also that the mass of the nega¬ 
tive electron and the charge on that electron are always invariable, 


i 


RADIOACTIVE SUBSTANCES. 


45 


regardless of the nature of the gas in the tube or the substance of the 
electrodes, while, on the contrary, the positive electrification is always 
found to be associated with a mass corresponding with an ordinary 
atom, and it varies with the different gases in which the electrifica¬ 
tion is found. 

The more recently discovered radioactive substances, such as ura¬ 
nium, thorium, polonium, and radium, are found to give out certain 
rays without any at present definitely known exciting cause. Radium, 
or rather a salt of that metal, such as radium bromide, is the most 
radioactive of these substances, and gives off at least three differ¬ 
ent kinds of rays, which Professor Rutherford has named the alpha, 
beta, and gamma rays. The alpha rays are feebly penetrating; the 
beta rays are deflected by a magnet and are akin to the cathode rays, 
that is, negative electrons thrown off at a high velocity; while the 
gamma rays are not deflected by a magnet, but are highly penetrating, 
like the Roentgen rays, affecting photographic ]flates, etc. 

The investigations of these phenomena indicate that all matter is 
similarly radioactive, but in the majority of cases the radiation is so 
slow or so feeble that no perceptible diminution of the substance would 
be measurable in millions of years, while in the case of the most radio¬ 
active substances the process is still so slow that, according to Becque- 
rel, the discoverer of radioactivity, a surface of one square centi¬ 
meter covered with pure radium would lose but .001 milligram of its 
xveight in one million years. From these facts, however, it is deduced 
that the processes of physical decay that are apparent to our senses all 
;about us are also going on in the disintegration of the atoms them¬ 
selves, and ultimately, unless there is a corresponding growth of the 
atoms, all matter will once more be resolved into “protyle.” 

Whether the electronic theory, which is in a measure a return to 
Newton’s corpuscular theory, will survive or itself will in turn be 
replaced by some other more suitable theory, remains for the future 
to determine. At present, the theory serves the purpose of giving a 
common origin to matter, electricity, and the ether, the electron being 
the common tie between them. 

The conception of the idea of a universal radiation of matter is 
attributed to M. G. Le Bon, who termed it “black light.’’ The 
present writer very crudely, at the time of the announcement of the 
discovery of the Roentgen rays, independently expressed the same 
idea, in a letter to the “Electrical Engineer,” New York. 




CHAPTEK VI. 

SYNTONIC WIRELESS TELEGRAPHY. 

At an early period of the practical history of wireless telegraphy 
it was seen that the usefulness of this art might be considerably cur¬ 
tailed by the fact that but one message at a time could be transmitted 
between any two stations within the sphere or radius of influence of 
a transmitter, since the attempt to send even two messages at once 
would render both messages unintelligible. A number of experi¬ 
menters have endeavored to overcome this defect, notably Dr. Lodge, 
Sig. Marconi, and Dr. Slaby. The plan followed by these gentlemen 
has been that of employing a syntonic or tuning method; that is, a, 
method by which the transmitting and receiving circuits are adjusted 
or attuned to a given rate of electrical oscillations. 

The explanation of this method may be simplified by a reference 
to the tuning-fork experiment already mentioned. As stated, either 
fork may be set into vibration by air-waves set up by the other fork, 
and neither will be set into vibration by another fork of a different 
pitch. As already noted, the ear and the telephone are quick to respond 
to vibrations and quick to stop vibrating. On the other hand, the 
tuning-fork is a persistent vibrator by virtue of two qualities which it 
possesses, elasticity and inertia. When struck a smart blow, or 
plucked, it is moved from its point of rest; directly its elasticity 
returns it to its normal position, its inertia or momentum carries it 
past that point, its elasticity returns it to zero point, inertia carries 
it past, and so on, until the resistance of the air and molecular fric¬ 
tion of the fork stop it. Analogously, an electrical conductor or 
circuit may be given, in almost any desired quantity, the equivalents 
of mechanical inertia, elasticity, and resistance or friction, in induc¬ 
tance, capacity, and ohmic resistance, respectively; and the rate of 
electric oscillation of a circuit may be varied by varying these factors- 
—the smaller the factors the higher the rate of oscillation. 


DAMPED AND PERSISTENT VIBRATORS. 


4? 


When the receiving circuit of a wireless telegraph system is accu¬ 
rately tuned to oscillate in harmony with the transmitting circuit, by 
giving the respective circuits practically equal inductance, capacity, 
and resistance, the receiving circuit will respond only to the oscilla¬ 
tions set up by a correspondingly attuned transmitter. This is, in 
brief, the theory upon which syntonic or tuned wireless telegraphy is 
based. In the original Hertz experiments, as has been noted in a 
previous chapter, the oscillation periods of the transmitter circuit and 
receiver or electric resonator were practically equal or in syntony. Mar¬ 
coni and others in their experiments have found that perfect syntony 
between the transmitting and receiving circuits is not essential, but 
that if there is a marked difference of frequency of oscillation between 
them the receivers will not respond to any but their correspondingly 
attuned transmitters. It was probably Sir 0. Lodge who first em¬ 
ployed the term “syntony” (equal or uniform tone) in connection 
with Leyden-jar experiments, and who also first devised a tuned trans¬ 
mitting and receiving wireless telegraph circuit (described subse¬ 
quently). 

It is perhaps not strictly correct to say that a tuned receiver will 
only respond to oscillations of its own periodicity. It may perform 
forced oscillations, if the exciting cause is sufficiently powerful, 
analogously as an elastic rod may be caused to move rapidly back 





Fig. 20. 



Fig. 21. 


and forth by the hand, but if pulled back and let go it will vibrate 
at its natural rate, which maybe termed free vibrations; and further, 
if it be struck blows at proper intervals its amplitude of vibration will 
be increased. In this latter case the principle of resonance enters, 
as it does also in tuned or syntonic wireless telegraphy, it being 
understood in the latter case that the “blows” consist of consecutive 
series of electric waves falling upon or cutting the receiving wire. 




































48 


WIRELESS TELEGRAPHY. 


Lodge, following Bjerknes, points out that an oscillator such as; 
was used by Hertz makes a good radiator of electric waves, but “in 
consequence of this its vibrations are rapidly damped (Fig. 20), and 
it only gives three or four good strong swings/’ and it follows from 
this that it will set up oscillations in conductors not at all in tune 
with it. On the other hand, the Hertz circular receiver or resonator 
is a “ persistent vibrator and well adapted for picking up waves of 
precise and measurable wave-length” (Fig. 21). (See Lodge’s “The- 
Work of Hertz,” pp. 4, 5.) 

It is known, also, that a vertical wire grounded at its lower end,, 
such as is used in wireless telegraphy, is an excellent radiator of elec¬ 
tric waves, but, as Marconi and others have pointed out, possesses- 
very little capacity, and hence its waves, like those of the Hertz radia¬ 
tor, are quickly damped, and it is only the first few oscillations that 
have sufficient strength to affect a receiver, but these strong oscilla¬ 
tions will, as just noted, affect almost any untuned conductor within, 
the range of their influence and set up aperiodic oscillations therein. 

These considerations led Marconi to experiment 
with conductors of larger size in order to obtain 
greater capacity, and, consequently, more persistent 
vibration, but this plan he found neutralized itself,, 
inasmuch as the greater surface gave increased 
facility for radiating the energy during the first 
oscillations. To avoid this defect Marconi availed 
of the fact that the capacity of a conductor is in¬ 
creased by bringing another conductor near it, and 
this without adding to the radiating surface of the 
first conductor. In the first experiments along this 
line he used an earthed conductor a' (Fig. 22), 
which was shorter than the transmitting wire a. 
Having thus added capacity to the wire, it was easy 
to add inductance to the circuit in the shape of a 
coil of wire i, and thus obtain a tuned and more persistent radiator. 
In the same way the receiving circuit similarly arranged becomes a more- 
persistent vibrator, and hence a given amount of energy expended at 
the transmitter in producing a succession of oscillations of more uni¬ 
form amplitude will have a cumulative or resonant effect upon the 
receiver and will eventually cause it to respond to the waves established 
by the transmitter, while an untuned receiving circuit containing a 






TUNED AND UNTUNED CIRCUITS. 


49 


detector fully as sensitive as the first one would probably not respond 
to those particular oscillations. 

In general the spark-gap and the receiving apparatus of untuned 
circuits are connected directly to earth, in series with the vertical 
wire A, as indicated in Figs. 23, 25, 26, and thus the oscillations set 
up therein are of short duration, being quickly damped. The appa¬ 
ratus and circuits of tuned circuits, on the contrary, are usually 
separated by a transformer t and condensers from the vertical wire, 
as indicated in Figs. 24, 27. In Figs. 23, 24, b b are the spark-balls; 
p, s are the primary and secondary wires of induction coil I. In 
Fig. 24 the spark-gap s, condensers c c , and the primary of the trans¬ 
former T, form a closed “ oscillating circuit,” in which the capacity 



Fig. 23. Open Circuit. Fig. 24. Closed Circuit. 


and inductance may be of a desired amount, and are generally so chosen 
as to give a wave-length equal to four times the length of the vertical 
wire. (See pp. 35, 56, 63, 95.) When the condenser discharges 
into this oscillating circuit, the oscillations are of more or less pro¬ 
longed duration, and oscillations of corresponding duration are set up 
by means of transformer T in the vertical wire, which in turn radiates 
electric waves of similar duration. 

The oscillating circuits of untuned wireless systems are termed 
“ open” circuits; those of tuned systems are termed u closed” cir¬ 
cuits. Figs. 23 and 24 are examples of “open” and “closed” trans¬ 
mitting circuits, respectively. It may be noted that open circuits are 
utilized in some systems in which syntony or tuning is not availed of. 
Further reference will be made to tuning, resonance, etc., elsewhere. 

Experiments have shown that by means of tuned apparatus a 
much greater distance may be covered with a given amount of elec¬ 
trical energy and height of wires. Thus, Marconi states that a 
transmitter which would operate a tuned receiver 30 miles distant 
would not affect a non-tuned receiver 160 feet away. This, it may he 
assumed, and as already intimated, is because in the case of the tuned 
receiver the faintest oscillations, or electromotive forces, set up in 











50 


WIRELESS TELEGRAPHY. 


the receiving circuit by the incoming circles of waves are in unison 
with those waves, and successive incoming waves resonantly amplify 
the oscillations, or electromotive forces, in the receiving circuit until 
they alfect the coherer; whereas, the oscillations which the same 
waves tend to set up in the non-tuned receiver are, as it were, out 
of step with the natural rate of oscillation of the non-tuned circuit, 
and thus as frequently oppose as assist the natural oscillations of the 
circuit, with practically a zero result. In tuned circuits it is there¬ 
fore essential that the makes and breaks or variations of the trans¬ 
mitter primary circuit should follow each other very quickly in order 
that the full effects of resonance may be obtained; in other words, that 
the wave-crest between successive series of oscillations may not fall 
too low for best results. Indeed, the inability to obtain successful 
syntony is partly attributable to the difficulty in obtaining a suffi¬ 
ciently close succession of series of oscillations with the transmitting 
devices hitherto employed, owing to the resistance of the spark-gap, 
which increases with the length of the spark, and doubtless also 
varies with the variations in the temperature of the arc, and thus 
either by excess of resistance quickly damps the oscillations, or by 
rapid variations in the resistance varies the rate of oscillations, 
since, according to Kelvin, the number of oscillations per second equal 




'JL_ 

LIv 


R 


— r, and when the resistance exceeds 


/■ 


4l 

K 


there will be 


2 7 t T lk 4l 2 

no oscillations, but only a dead-beat discharge. Further, with the 
present type of transmitting devices a long spark-gap appears to be 

essential to the employment of high potentials in long-distance trans- 

♦ 

mission. See in this relation air pressures at spark-gap, p. 166. The 
varying resistance of the filings coherer is also an impediment to the 
maintenance of syntony in the receiving circuit. Inasmuch, there¬ 
fore, as it is easy to design the fixed apparatus and circuits of a wire¬ 
less system to have almost any desired inductance, capacity, and 
resistance, it is in the directions mentioned that improvements in 
syntonizing may be expected. Already it has been suggested that a 
device such as that of Cooper Hewitt’s, described in the section on 
interrupters, may be available for this purpose, and Marconi and 
others have pointed out that detectors of the magnetic type (see p. 71), 
by reason of their practically uniform resistance, and in other ways, 
may permit of more accurate tuning. 

By the aid of electric syntony it is expected that it will be pos- 





TUNED CIRCUITS. 


51 


sible to send several messages between the same points at the same 
time without interference, by allotting different rates of oscillation 
periods to different sets of transmitting and receiving apparatus. It 
is also expected that one vertical wire will suflice for all the apparatus 
at one station. To those who are familiar with Gray’s harmonic 
system of wire telegraphy (described in “American Telegraphy,” 
p. 3 ooa, 1903 edition), in which three and four instruments, attuned 
to tiansmit and to receive different rates of electrical current pulsa¬ 
tions, have been successfully operated on one wire at the same time, 
this will not seem impossible if it be found that practical tuning is 
feasible. It is also quite possible that if a universal receiver like 
the telephone be employed, it will be feasible to receive a number of 
different tones at one and the same time in the one instrument, as 
has already been done in wire telegraphy. (See “Electrical World,” 
October 6, 1888). It is known that the telephone can also be syn¬ 
tonized, and in fact has been proposed by M. Mercadier as a one tone 
instrument, adjusted to respond to a given rate of pulsations per 
second in multiplex telegraphy; and by Professor A. Blcndel to 
respond to the frequency of charging the vertical wire; in other 
words, to the rate of interruption of the induction coil, in which case 
one, two, or more such telephones, each attuned to respond to a dif¬ 
ferent rate of charging of the transmitting antenna?, may be placed 
directly in the circuit of the receiving antenna?, analogously as in 
the case of the harmonic system cited. Or they may be placed in 
shunt with a more sensitive detector, the latter being in series with 
the vertical wire. Here the chargings, or groupings, of waves, and 
not the oscillations proper of the antennae, constitute the important 
feature. But, it may be noted, combinations of both features have 
been suggested. Thus far, however, it does not appear that more 
than one message at a time has been received at one station, except, 
perhaps, experimentally; and if the ill success and abandonment of 
Gray’s harmonic system, after a long trial on wires, be any criterion, 
multiple wireless telegraphy between two given points will prove a 
difficult problem, although not an impossible one. But if by the 
lise of tuned apparatus nothing else were gained than the ability, 
with a given amount of electrical energy and a given height of ver¬ 
tical wire, to transmit signals to a greater distance than is possible 
with untuned apparatus, it would be a decided advance in the art. 


CHAPTER VII. 

MARCONI WIRELESS TELEGRAPH SYSTEMS, 

TUNED, UNTUNED, AND LONG DISTANCE. 

MILITARY AND LIGHTSHIP STATIONS—MORSE ALPHABETS, ETC.. 

The distinction between tuned and untuned wireless telegraph* 
systems has been noted in connection with the chapter on syntonic 
wireless telegraphy. 

The Lodge experiments of 1894 were followed by the experiments 
of Marconi a year later. The principal apparatus employed by Mar¬ 
coni in his original experiments consisted of an oscillator and a verti- 
cal wire at the transmitting station, and a filings-coherer, relay and 
tapper, and vertical wire at the receiving station. These devices, as 
previously intimated, were known to the art, but they were all more 
or less modified by Marconi, who also added other devices as found 
requisite to bring his system to a point of practical utility. 

The earlier arrangement of apparatus employed by Marconi is 
outlined in Figs. 25 and 26. In Fig. 25, I is the induction coil 
of the oscillator; b b' are the discharge-balls, between which is the 
spark-gap; K is a Morse key of heavy construction; b is a storage 
battery of about 5 cells. The vertical wire a, or antennae, is con¬ 
nected at its lower end to ball b; the other ball, b\ is connected to 
earth. The balls b V of the oscillator are thus in series with the 
aerial wire. The terminals w tv' of the secondary wire s s of the 
induction coil are also connected respectively to b and b'. 

The type of oscillator first employed by Marconi was that known 
as the Righi oscillator, which, in addition to the ordinary induction 
coil, consisted of two metal balls about four inches in diameter, con¬ 
nected with the terminals of the secondary wire of the induction 
coil. These balls and the spark-gap were immersed in oil in a suita- 


MARCONI UNTUNED SYSTEM. 


53 


ble receptacle, with the object of obtaining a sharper break and 
consequently a more efficient spark. The oil was also found to pre¬ 
vent the necessity for frequent cleaning of the balls. The oil-inclosed 
balls have, however, been abandoned in subsequent tests, and balls 
about one inch in diameter are now used. With a six-inch coil, the 
electric waves set up by this oscillator were about ten inches long. 





Fig. 25. 



Fig. 26. 


The actual transmission of messages is effected by means of key k_. 
Each time the key is closed the vibrator a starts into operation, with; 
the result that electric oscillations are set up in the aerial-wire circuit 
and electric waves are emitted. When the key is opened the oscilla¬ 
tions cease, and in this way the duration of a train of waves or oscil¬ 
lations is made to correspond to dots and dashes of the Morse alphabet. 

The receiving apparatus is indicated in Fig. 26. h is the Marconi 
coherer. It consists of a glass tube, properly supported, about 1.57 
inches in length, and about .1 inch inside diameter. Small silver 
plugs w, of a size to snugly fit the tube, are inserted as indicated. There 
is a small space of about .05 inch between their ends. The filings 
are placed in this space. The plugs must so fit the tube that the 
filings cannot be scattered between the sides of the glass and the 
plugs. A comparatively small number of filings suffice. Marconi 
uses ninety per cent, of nickel and ten per cent, of silver filings, but this 
proportion may be varied as greater or less sensitiveness is desired, 
the sensitiveness increasing with an increased proportion of silver 
filings. Wires are led in from each end of the tube to the plugs,. 














































54 


WIRELESS TELEGRAPHY. 


and, to prevent oxidation of the filings, the tube is exhausted of 
air to about one thousandth of an atmosphere, after which it is her¬ 
metically sealed. T is a tapper; r is a sensitive relay—it may be a 
Morse or polarized relay; E is an ink recorder with paper reel, etc. 
(described in “American Telegraphy,” p. 70). The vertical wire A 
is connected to one terminal of the coherer, the other terminal of 
coherer is connected directly to earth. Relay R is in a local shunt 
circuit with the coherer and one cell of battery b. The armature- 
lever l of this relay controls the local circuit of the tapper and also of 
the ink recorder E, which circuits are fed by the local battery b\ consist¬ 
ing of four or six cells, k represents actual appearance of the coherer. 

The operation of this apparatus is briefly as follows: When the 
electric waves set up by the distant transmitter arrive and oscillations 
are thereby set up in a, the resistance of the coherer k drops suffi¬ 
ciently to allow battery b to magnetize relay r, which attracts its 
armature, closing the circuit of b' at x\ as already described in con¬ 
nection with Fig. 12. Hence, while the oscillations are being received 
the tapper keeps up a buzz or hum, and stops when the oscillations 
cease. So, also, while the oscillations continue the Morse inker e is 
actuated, and a dot or dash, as the case may be, is impressed on the 
paper strip. The paper strip is started and stopped automatically by 
devices well known in telegraphy, when signals commence and when 
they cease. (See “American Telegraphy,” p. 373.) 

In addition to the apparatus outlined in Fig. 26, a number of 
inductance or impedance “choke” coils ck ck and non-inductive 
shunt coils, essential to the practical operation of the system, are 
employed. The choke coils are furnished with iron cores to increase 
the magnetic effect, and are wound straight; the non-inductive coils 
are wound back upon themselves, and are thus rendered non-magnetic, 
offering resistance only to the current. Further details of these coils 
will he given shortly. 

In a later arrangement Marconi introduced an induction coil or 
transformer, termed, in shop phrase, the jigger, between the vertical 
wire and the coherer, theoretically shown in Fig. 27, in which p is 
the primary wire of the transformer. The secondary wire is divided 
into two sections a* s, as indicated, the coherer k being placed between 
them. A condenser c is placed as shown, forming a short circuit 
for the secondary oscillations to the coherer (for momentary cur¬ 
rents a condenser is virtually a conductor), ck ck' acting as choke 


DETAILS OF THE JIGGER. 


55 


coils, directing the oscillations across c, and preventing any dissipa¬ 
tion of the current through the relay, which is made with as little 
self-induction as possible. 

According to Marconi, these choke coils consist of a few inches of 
fine copper wire wound over a bit of iron wire 1.5 inches in length. 
The coils of the jigger, shown as J in subsequent 
figures, are wound over a small glass tube .3 inch 
in diameter. The secondary consists of 375 turns 
of copper wire about .002 inch in diameter, insu¬ 
lated with one covering of silk and having a resist¬ 
ance of 79 ohms. The primary is wound over the 
secondary, has 175 turns of wire about .0047 inch, 
and a resistance of about 7 ohms. Another form 
of jigger, as described by Marconi, is virtually as 
follows: The primary is wound on an ebonite or 
glass tube about .22 inch diameter. It consists 
of 100 turns of copper wire .014 inch diameter, 
about 4.5 ohms resistance, insulated with silk 
and coated with paraffin wax. The secondary is 
of copper wire .007 inch diameter, also insulated with silk. It is 
wound over the primary. The secondary is in two parts. Each half 
of the secondary is made up of 17 layers of wire, with a gradually 
decreasing number of turns in each layer, 77, 49, 46, 43, 40, 37, 34, 
31, 28, 25, 22, 19, 16, 7, 3, respectively, making 500 turns in all, 
with a resistance of about 23 ohms. The condenser c is composed of 
twelve small tin-foil or copper plates connected in the ordinary way 
and insulated with paraffin paper. The plates, in size, are about 
2 inches by 1.2 inches. Small Leyden jars are also used. It is 
claimed that the induction coil or jigger J, acting as a “step-up” 
transformer, largely increases the efficiency of the apparatus by 
enhancing the electromotive forces acting upon the coherer, and thus 
increases the signaling distance. Further, it measurably protects the 
apparatus against atmospheric electric currents (which would otherwise 
be more or less detrimental to the operation of the coherer), by giving 
these currents a practically direct path to earth. 

In a system undergoing so many modifications as that under con¬ 
sideration, no fixed arrangement of apparatus can be expected for every 
station thus far equipped with this system. One practical arrangement 
of the Marconi transmitting and receiving apparatus is, however, shown 




















56 


WIRELESS TELEGRAPHY. 


diagrammatically in Fig. 38. In practice it is found advisable to 
inclose the coherer k, jigger /, relay R, tapper t, and the wires con¬ 
nected therewith, in a metallically sheathed box b. This sheathing is 
connected to ground as at G. Since electric waves do not pass through 
metals, extraneous waves are, by this device, prevented from affecting 
the coherer. R is the relay controlled by the coherer; ck ck are the 
•choke coils in the circuit of r; b is a single cell for the operation of 



R. R is a sensitive polarized relay of from 1200 to 10,000 ohms resist¬ 
ance, and is usually inclosed in a cylindrical case to exclude dust. It 
is known that the coherer decoheres more readily with a weak cur¬ 
rent than a strong one, hence a sensitive relay is desirable. Some of 
the relays employed will act with a current of -g-ol o'-o of an ampere. 
In order that a weak current may be obtained a resistance is some¬ 
times placed in the circuit of b. A further reason for the use of 
a sensitive relay is that with a strong current the coherer may act 
continuously. 

It is essential that no sparks shall be developed at any of the 
contact points of the relay R or the tapper t , as the oscillations 
coincident with such would affect the coherer. To prevent such 
sparks and oscillations the magnet coil of the tapper t is shunted by 
a non-inductive resistance w of 1000 ohms, its contact points a with 
.a similar resistance x. The contact point / of relay R is shunted by 













































































































DETAILS OF MARCONI SYSTEM. 


57 


ji non-inductive resistance y of 4000 ohms, also with a condenser c', 
which has in its circuit a resistance of 500 ohms. It will be seen 
that one terminal of battery b' is earthed at g. The ink recorder e 
(resistance 400 ohms) is placed outside of box b, and, together with 
tapper t , is operated by battery b\ and controlled by the armature of 
relay r. The tapper is in a metallic circuit. The ink recorder is in 
a ground return circuit, from ground at G through b\ through lever l 
to/, through the sheathing of the box to E and earth. Recorder E 
is also shunted by a non-inductive resistance r of 1000 ohms. In order 
that no stray electric waves may enter the box by the wire to e, that 
wire is caused to pass through an inductive coil or choke coil c J 
placed on the side of the box. For this purpose Marconi first em¬ 
ployed a coil of about 4 ohms or 125 turns of No. 28 wire, insulated 
with gutta-percha and covered with strips of tin-foil which are con¬ 
nected to the metal sheathing of the box. In later experiments a coil 
of 45 ohms has been used by others. The coil is carefully protected 
against mechanical injury. A call-bell cb is controlled by the lever 
of e, and is shown as operated by a separate local battery lb. One 
terminal of the primary coil p of the jigger J is grounded by contact 
with sheathed frame b; its other terminal goes to an insulated open¬ 
ing m in the box b. Here in some cases it is provided with a movable 
connection which places it in contact with the back contact of trans- 
mitting-key k, and in practice this movable contact consiscs of an 
arm, not shown, from the key K, which is inserted at m for “receiv¬ 
ing,” but is removed therefrom for “sending,” by which means the 
box is entirely disconnected from the transmitter. In other cases the 
key is connected practically as shown, the air-space between the front 
and back of the key being sufficient to insure that no damage may 
occur to the receiving apparatus from the high potentials of the 
transmitter, the key having an up-and-down motion of several inches. 
The box b is made in two parts and can be readily opened for inspec¬ 
tion and adjustment of the apparatus. 

The transmitting apparatus is shown at the left of figure. K is a 
massive Morse key (rendered necessary by the heavy currents and 
high pressures used in the oscillator^circuits) with front and back 
■contacts, which are well insulated from each other. The key is 
provided with a large ebonite handle h. Its front contacts u are 
shunted by the condenser n. The lower contact is in an earthed 
metal cup u\ by which device high potential charges are diverted 


58 


WIRELESS TELEGRAPHY. 


from the key. The interrupter i of the induction coil is also shunted 
with a condenser q; i is the induction coil of the oscillator; SB is a 
storage battery for the operation of the induction coil. It will be 



Fig. 29. General Arrangement of Marconi Apparatus. 

seen that it is controlled by the front contacts of k. dc are dry 
cells in multiple which charge the storage cells. A switch is usually 
inserted at s whereby the battery may be cut off, reversed, etc. 

The general arrangement and 
appearance of the more impor¬ 
tant apparatus used in the Mar¬ 
coni and other systems are illus¬ 
trated in Fig. 29, in which b is 
the box containing the coherer, 
relay, etc.; e is the ink record¬ 
ing register ; r is the reel for 
carrying the paper strip on 
which the message is recorded; 
l is a battery of Leyden jars or 
condensers; i is the induction 
coil and discharge-knobs; k is 
the Morse transmitting-key; G G 
are ground connections; v is the 
vertical-wire terminal. The ap¬ 
paratus occupies a space of about 
4.5 by 2.5 feet on a table which 

is usually covered with sheet rubber. 

The vertical wire or wires for ships, and for comparatively short 
distance signaling, is usually of stranded copper, about .25 inch in 



Fig. 30. Shore Station. 










































































LIGHTSHIP AND FIELD STATIONS. 


50 


diameter, although Marconi has used also strips of wire netting about 
two feet broad. The wire or netting is supported by masts of proper 



Fig. 31. Lightship Station. 


strength and height, securely guyed, as indicated in Figs. 30, 32, 
which represent a wireless telegraph shore station and a military 
wireless telegraph outfit respec¬ 
tively. Some of the masts used 
for this purpose weigh over five 
tons. It is not essential that the 
wire be suspended strictly verti¬ 
cally if the necessary vertical 
height be obtained. Obviously, 
vertical masts several hundred 
miles apart will not, owing to 
the curvature of the earth, be 
parallel to each other. The wires 
must be insulated from the mast 
or tower by which they are sus¬ 
pended, otherwise in wet weather 
the electric charges would be dis¬ 
sipated to earth. Inasmuch as 
the electromotive force thrown 
on these wires is frequently suf¬ 
ficient to produce sparks of six, Fig. 32 Field Wireless Telegraph. 
twelve, or more inches, it is evi¬ 
dent the insulation must be thorough. For this reason the wires 
are separated from the masthead by long sticks of ebonite (a. 










































































































































GO 


WIRELESS TELEGRAPHY. 


Fig. 31), and, when feasible, are led in through an open window 
or hatchway to the room where the transmitting and receiving appa¬ 
ratus are situated, as outlined in the same figure which repre¬ 
sents the lightship at Nantucket Shoals, ofi; Massachusetts, equipped 
with the Marconi wireless telegraph system. At this latter station 
passing vessels are reported daily, and messages are transmitted and 
received between them and the lightship by wireless telegraphy when 
vessels are equipped with the necessary apparatus. When this is not 
the case, messages may be sent or received by means of steam-whistle 
or fog-horn, the continental Morse code being used for this pur¬ 
pose, a long and short blast corresponding to the dot and dash of 
that code, which code is given at the end of this chapter. Messages 
thus received are then forwarded from the lightship by wireless teleg¬ 
raphy to the mainland. 

Another method of bringing the vertical wfire into the operating- 
room of a ship is outlined at s in Fig. 28. A hole about four inches 
in diameter is made in the deck. This is sheathed with a tube of 
ebonite half an inch thick, which rises about 1.5 feet from the sur¬ 
face of deck, and is protected from mechanical injury by a thick brass 
sheathing. Through the center of this opening the vertical wire is 
led after it has been thickly insulated with india-rubber strips and 
oiled silk. The space between the ebonite tube and the vertical wire 
is filled with an insulating compound such as paraffin, and the tube 
is then capped with ebonite. Below this tube the insulation of the 
wire is gradually tapered off until it somewhat resembles a tail, v, 
from which fact this portion of the vertical wire has been dubbed the 
“cow’s tail” (see Figs. 28, 29). Two wires are led from this wire, 
one to a ball V of the oscillator, the other to the key or keyboard, as 
shown. The other ball b of the oscillator is connected to earth. On 
shipboard the ground or “earth” is taken from the metal plates of 
the vessel, the ground wire being riveted or otherwise clamped securely 
to a plate of the framework of ship. 

In Fig. 33 is given a facsimile of messages “caught on the wing” 
during the yacht races of 1899 off New York Harbor. Bulletins of 
the progress of the race were being sent from the steamship Ponce to 
the Mackey-Bennett cable ship some miles away, both equipped with 
Marconi apparatus, when this specimen and many others were recorded 
by a set of wireless telegraph apparatus constructed by Mr. W. J. 
Olarke, which the writer was supervising on the steamship La Grand 


MARCONI SYNTONIC WIRELESS SYSTEMS. 


61 


Ducltesse. This was probably the first instance of tapping Hertzian 
waves, in the United States at least. Abbreviations, such - Shr. for 
Shamrock , Col. for Columbia , the competing yachts, Uk for about. 



H 




R 


A 


W 



A 



A 


Fig. 33. 



bd. for board, etc., were used in these despatches. The universal or 
continental alphabet was employed. 

With the filings-coherer thus far described the speed of transmis¬ 
sion is limited to twelve or fifteen words per minute, the cohering, 
tapping back, recording of the message, etc., all tending to slow 
speed. The type of key shown is also essentially a slow speed key. 
The degree of sensitiveness of the relay may be tested by shunting 
the coherer with a low resistance, such as a moistened string or fin¬ 
gers, when, if the relay is too sensitive, the tapper will vibrate. In 
that case the adjustment of the relay should be varied. On the okier 
hand, this result may arise from a defective coherer, one of too low 
resistance initially, in which event it should be replaced by a perfect 
instrument. To test the general operativeness of the receiving appa¬ 
ratus a small electric buzzer is sometimes used in the vicinity of the 
vertical wire. Experience has demonstrated that the adjustment of 
this apparatus is not always easily obtained, and hence when obtained 
should not be needlessly varied. When an “exhausted’’ coherer 
becomes inoperative it cannot be restored to working condition. For 
this reason, among others, it is usual to keep a liberal supply of extra 
coherers on hand. 


MARCONI SYNTONIC WIRELESS SYSTEMS. 

One arrangement of Marconi’s syntonic transmitting and receiving 
circuits is outlined in Figs. 34, 35, the tapper, shunt coils, etc., being 
-omitted for simplicity. Fig. 34 represents the transmitting circuits. 
A is the vertical wire attached at its lower end to a coil of wire w, 
which is connected to ground. One terminal of the secondary wire s 
of an induction coil t may be connected to any desired turn of the 
coil tv. By this means the inductance of the vertical-wire “open” 
circuit may be varied and its oscillation period thereby be made to 
correspond with that of the “closed” circuit o of the oscillator, 
which includes the primary wire p of t. i is the induction coil; c is 














62 


WIRELESS TELEGRAPHY. 


an adjustable condenser of about .25 m.f. capacity, by varying which the 
oscillation period of the closed circuit may readily be varied. Leyden 
jars are often used for this purpose. The capacity is varied by 
moving inward or outward one or more plates of the condenser, or by 
adding or removing one or more of the Leyden jars. An adjustable 
capacity, not shown in figures, may also be placed in the vertical wire 
at A to facilitate tuning. The period of oscillation is increased by 




Fig. 35. 


adding turns to coils w , and decreased by reducing the number of 
turns. The period is also decreased by adding to the capacity of a 
condenser in series with w, and vice versa. The various circuits will 
be in tune when the product of the capacity and inductance of each 
circuit is equal, since the period of a circuit is equal to 2?r times the 
square root of the product of inductance and capacity. 

The tuned receiving circuits are shown in Fig. 35. a is the ver¬ 
tical wire with the turns of wire w, to which is attached the primary 
wirejt? of the induction coil or “ jigger '’ t. It is important that the 
oscillation period of the coherer circuit shall be the same as, or an 
octavo of, the vertical-wire circuit. This, according to Marconi, may 
be done by making the secondary coil s s of the coil T equal the length 
of the vertical wire a, in which case, as this coil lias practically no 
capacity, while it may be assumed to have equal inductance with the 
vertical wire, its wave-length will be virtually one half of that wire, 
and its rate of oscillation will be an octave above it. The transmitter 
circuit is then adjusted so that its period corresponds with that of 
the receiving circuit. This is done by varying the capacity of the 
condenser c. The receiving condenser c consists of a few sheets 
of copper or tin-foil separated by thin sheets of paraffin paper, the 
alternate metal pla'es being connected together. The manner of 








































MARCONI CYLINDER ARRANGEMENT. 63 

obtaining this “ balance ” is to begin with very little capacity in the 
condenser and auding plates until the best results are obtained at 
the receiving station, when if more capacity is added to the condenser 
the signals die away, showing that the circuits are now out of tune. 

The inductance may be readily varied—that is, turns of coils w 

may be cut in or out by means of the sliding contacts shown in 
Figs. 34, 35, 36. 

Marconi Cylinder Arrangement.—Another device due to Marconi, 
and which is also used in connection with tuned circuits, is shown in 
Fig. 36. In this arrangement the high vertical 
wire at each station is replaced by concentric metal 
cylinders A, the outer one of which is about 4 feet 
high and 1.3 feet in diameter. With this device 
signals have been transmitted over 31 miles. The 
outer cylinder is connected to the inductance wire 
w , the inner one to earth. The other connections 
are practically similar to those shown in Fig. 34. 

In other instances cylinders about 20 feet high 
and 5 feet in diameter have been used. The 
cylinders can be carried on a steam motor car 
and lowered when desired. In this case the earth connection is made 
by trailing a strip of wire netting on the ground; here a compara¬ 
tively loose earth connection suffices. The cylinders as thus ar¬ 
ranged form in effect two plates of a Leyden jar, or condenser, 
giving a large capacity, thereby providing a persistent vibrator, inas¬ 
much as this property is increased in this arrangement in a greater 
ratio than its radiating property, and, as has been suggested, perhaps 
the proximity of the plates Also tends to add magnetic energy to the 
circuit; these causes doubtless operating to give the device a very 
definite period of oscillations, for in practice it has been found to 
work successfully as a selective syntonic apparatus. 

It was found essential in practice that the inductance of the inner 
cylinder should be less than the outer one and this was at first 
secured by making the earthed cylinder the shorter of the two, but 
subsequently the same result was obtained by the use of the induct¬ 
ance w, attached as shown, or placed between the spark-gap and the 
outer cylinder. Marconi considers that this inequality of inductance 













64 


WIRELESS TELEGRAPHY. 


is necessary to put the two cylinders out of phase, as otherwise the 
one would neutralize the effect of the other, hence no radiation 
would take place. 

MARCONI LONG-DISTANCE WIRELESS TELEGRAPH. 

The general means hy which long-distance transmission has been 
accomplished are increased electrical energy at the transmitting sta¬ 
tion and more sensitive apparatus at the receiving station, together 
with the employment of high towers or masts, and a multiplicity of 
aerial wires at the transmitting stations. 

The first station equipped for long-distance service was that at 
Poldlm, Cornwall, England, the next at Glace Bay, Cape Breton, and 
the third at South Wellsfleet, Mass. In the first long-distance tests 



Fig. 37. South Wellsfleet Station. 


at Poldhu there were two masts about 160 feet high and 200 feet, 
apart. Between the tops of these masts a wire was strung from which 
50 uninsulated wires were suspended. These wires converged at the 
bottom and were thence led into the instrument-room. Subsequently 
the long-distance stations were equipped with high masts arranged in 
a wide circle, with vertical wires depending from horizontal wires 
attached to the tops of the masts. This construction, however, was 
not of sufficient strength to resist storms, and in the later arrange¬ 
ments massive towers have been built. The arrangement depicted 
































































flemin?* transmitting system. 65 

in Fig. 37 is that of the South Wellsfleet station. Here there are 
four towers constructed of wood in the manner indicated. These 
towers are about 220 feet in height and stand on a sand cliff about 
150 feet above sea-level. A large number of small copper wires are sus¬ 
pended vertically from horizontal wires strung from tower to tower, 
as shown. The vertical wires converge as indicated when they are 
led into the operating-room; they are carefully insulated at the top 
from the wooden towers. 

Full details of the arrangement of these stations are not yet 
obtainable. At the Poldhu station it is understood that a 20-kilo¬ 
watt generator developing 2000 volts was used, and more powerful 
generators will be used in subsequent long-distance tests. This 
voltage is raised by “step-up” transformers, a type of induction coil, 
to perhaps 100,000 volts on the aerial wire. As previously intimated, 
owing to the losses in transformation and at the spark-gaps only a 
small fraction of the energy of the generator is radiated. It is clear 
that means must be provided for obviating danger and damage at the 
opening and closing of the transmitting key when strong currents and 
high potential are used. This is sometimes done by opening the circuit 
in oil, by blowing out the spark, etc., special keys and devices being 
used for the purpose, some of which will be described or mentioned. 

The Fleming Long-Distance Transmitting System.—One of a 
number of systems designed for long-distance wireless signaling by 
Prof. J. A. Fleming for the Marconi Wireless Telegraph Company is 
shown in Fig. 38, the following account of which is abstracted, with 
some changes, from the British patent specifications No. 3481, covering 
the same. In the figure, D is a 20 or 25 kilowatt alternator develop¬ 
ing 2000 volts more or less, with a frequency of 50 per second; T is 
a transformer, or several transformers in parallel, the primaries of 
which are in series with d. It may be noted that the coils of this 
and other transformers outlined in the cuts herein are wound one 
over the other, or end to end, in the usual way, although shown con¬ 
ventionally as separated in the figures for the sake of clearness. The 
transformer t raises the E. M. F. to about 20,000 volts, charging 
condensers c, which thereupon discharge across spark-gap s, in the 
secondary of T. Oscillations of a higher order are thus set up in the 
primary of t', which oscillations are again transformed to higher 
voltage in the secondary of t', charging condenser or condensers c', 
which discharge across spark-gap s', setting up oscillations in the pri- 


06 


WIRELESS TELEGRAPHY. 


mary of t*, which further increases the E. M. F. thrown upon the 
vertical wire or wires a. By means of this double or treble trans¬ 
forming the E. M. F. upon the aerial wires is sufficient to give a 




A 



0 



Fig. 38. Fleming’s Transmitting Arrangement. 


spark of about twelve inches, or, as stated, an E. M. F. of about 
100,000 volts. When it is desired to reduce the E. M. F. and fre¬ 
quency the oscillator circuit o' and transformer •T 2 are omitted and 
the secondary of transformer t' is connected to the aerial wires. 

Condensers c are of special construction, consisting of a number 
of stoneware boxes filled with double-boiled linseed oil, in which 
20 glass plates, 15.5 inches square and coated with tin-foil on both 
sides, are placed. Eighteen such boxes in parallel give a total capac¬ 
ity of about one microfarad. These condensers are connected as shown 
at C in such a manner that the total length around and through any 
condenser and the spark-gap and primary t' shall be equal, to the 
end that all condenser discharges shall travel in the same time to 
spark-gap s and all have the same frequency. 

The tuning of these circuits is effected practically in the following 
manner: The primary of transformer T 2 consists of seven No. 16 cop¬ 
per wires in a rubber-covered cable, wound once around a square or 
round wooden frame 18 inches in diameter, 7 to 10 of the strands 
being in parallel. The secondary of T 2 consists of 8 to 10 turns of 
the same cable wound over the primary. The condensers c' are so 
adjusted that circuit o', consisting of s', c', and primary of T 2 , has a 
period equal to the aerial wire and the secondary of t 2 . To bring 
about this result, a hot wire voltmeter suitable for measuring 3 to 5 
volts has its terminals placed to a piece of cable about two feet in length, 
which is inserted in the circuit of A and the secondary of t 2 . Oscil- 





















































TUNING CIRCUITS. 


67 


lations in the aerial circuit heat the voltmeter wire and cause a 
deflection of its needle. The exact size and length of cable to obtain 
a suitable deflection are ascertained by trial. Then if the capacity 
of c' be altered it is found that there is a certain capacity correspond¬ 
ing to which the oscillations in the aerial circuit are a maximum, as 
indicated by the voltmeter. The aerial circuit and first oscillator 
circuit o s are then tuned. The oscillation circuit of o s is then 
tuned to oscillation circuit o' s' by placing an adjustable inductance 
coil in the circuit between the secondary of t' and the discharge-gap 
s', and varying this inductance until the secondary spark is as long 
as possible. The circuit of the alternating current transformer T and 
the condenser C are then tuned by varying the number of trans¬ 
formers T joined in parallel, and the frequency of the alternations by 
varying the speed of the motor until the spark at s is as long as pos¬ 
sible consistent with its remaining an oscillatory spark. 

To obviate directly opening and closing the primary circuit of the 
alternating current transformer t , two choke coils i i\ having mova¬ 
ble iron cores m are placed in that circuit as outlined. The iron 
core of m' is so adjusted that as much current as can safely be passed 
through the primary of T shall normally flow in the circuit. The 
core m of i is let all the way down, and it entirely impedes the flow 
of current in the primary of T, by reason of its inductance. The 
latter coil, however, can be short-circuited by key K, at which times 
the current in said primary circuit attains normal value. Thus the 
circuit is not opened in the usual sense. But to avoid sparking key K 
is of a type that is opened at a number of places, ten or twelve, and 
the switch is opened in insulating-oil. 

In another patented device, due to Fleming, to avoid danger due 
to a sudden make and break in the primary of an alternating trans¬ 
former, the circuit is kept closed and blasts of air from a tube or 
nozzle controlled by a spring or string attached to a signaling key are 
directed against the spark-gap, thereby interrupting the sparks in 
accordance with the movements of the key. For particulars of other 
variations of the apparatus described reference may be had to the 
patent specifications. 

The vivid sparks and loud noises accompanying the operation of 
this and similar high potential transmitting apparatus has led to 
the application of the term “thunder factories ” to long-distance 
wireless telegraph stations. 


68 


WIRELESS TELEGRAPHY. 


ANTI-COIIERERS, AUTO-COHERERS, AUTO-DETECTORS. 

As previously remarked, had the progress of wireless telegraphy 
rested with the discovery of the Hertz detector, the utility of electric 
waves for the purpose of telegraphy would have been very limited. 
It might now he said that if the development of this art had stopped 
with the discovery and utilization of the Branly filings-coherer, the 
distance to which messages could be successfully transmitted would 
have been limited to perhaps 400 or 500 miles, and the rate of signal¬ 
ing to perhaps ten or twelve words per minute, for the action of the 
filings-coherer is inherently sluggish in the production of perfect 
signals, the cohering and “ tapping back/’ together with the mechan¬ 
ical inertia of the moving parts of the tapper, relays, etc., all tending 
to that result. Doubtless the distance mentioned as the probable 
commercial limit of signaling by the filings-coherer could be increased, 
as Marconi’s 'xperiments have shown, by the use of higher masts at 
both stations and an increased number of wires, and greater electrical 
energy at the transmitting station, but this would very likely be at 
the expense of a reduced speed of signaling. 

It was therefore obvious to all concerned in the advancement of 
wireless telegraphy that the production of a coherer or other form of 
detector which would be more sensitive and reliable than the filings- 
coherer, and one which would, so to speak, “close” on the occur¬ 
rence of electric oscillations in its circuit, and “open” automatically 
when the oscillations cease, and vice versa, was a thing much to be 
desired. As nearly always happens in such cases, this desideratum, 
or an approximation thereto, was not long in forthcoming. 

Perhaps the first automatic or “ self-righting ” coherer, produced 
was the carbon auto-coherer of Tomassini. It consists of powdered 
carbon, such as is used in microphone transmitters, placed in a small 
circular opening in a sheet of ebonite one tenth of an inch thick. r I his 
was found to cohere in the presence of electric oscillations and to deco¬ 
here without shaking on the cessation of the oscillations. 

Another auto-coherer was that devised independently by Neug- 
schwender and Aschkinass. This is a device in which scratches are 
mnde across the silvered back of a glass mirror. The mirror thus 
streaked is made part of an ordinary cohering circuit including a 
small battery and galvanometer. When moisture is thrown upon the- 
streaked portion of the glass, for instance by the breath or other- 


THE SOLARI AUTO-COHERER. 


69 


wise, the needle of the galvanometer is deflected. In this condition, 
if electric oscillations are set up in the circuit the needle returns to 
zero, and when the oscillations cease the needle is again deflected. 
The normal resistance of this arrangement is about 50 ohms; under 
the influence of electric oscillations it runs up to 80,000 ohms. Its 
action is thus opposite to that of the filings-coherer; hence it and 
other coherers of this type are termed anti-coherers. 

Another somewhat similar type of anti-coherer, due to Schaefer, 
consists of a silvered glass across which scratches or slits are made. A 
film of celluloid is then placed over the scratches, when it is found 
that under the influence of electric oscillations the resistance of the cir¬ 
cuit rises and decoheres automatically as in the case previously cited. 

It has been surmised that the effect of the film of celluloid, which 
does not penetrate into the interior of the slits, is to prevent the dis¬ 
sipation of the particles of silver in the slits, and whose motion, under 
the influence of the electric oscillations, probably accounts in a measure 
for the variations in the resistance of the circuit. These devices, 
however, were not used in actual practice. 

The next most important auto-coherer was probably that due to 
Solari, which was known for a time as the “ Castelli ” coherer, also as 
the Italian navy coherer, and was used by Marconi in some of his 
transatlantic experiments, to which further reference will be made. 
Within the past two years several other types of auto-detectors have 
been devised by different workers in this field, namely, Marconi in 
Europe and De Forest and Fessenden in this country. Owing to the 
sensitiveness of these auto-coherers, a 
telephone receiver is generally used in 
connection with them in place of the 
relay used with the filings-coherer. 

The Solari Auto-Coherer.— This 
auto-coherer is shown in Fig. 39. It 
consists of a thin glass tube &, 1.7 



inches long, suitably supported; c is 

a carbon rod or block; i is a plug of iron. A small drop of mer¬ 
cury w, not filling the space, is placed between c and i. A telephone 
receiver t and one cell of battery b are connected in circuit with the 
coherer, as shown. The E. M. F. of the cell should not exceed 
1 to 1.5 volts. For untuned circuits the connections are virtually as 
in figure, a representing the connections to aerial wire, E those to 


















70 


WIRELESS TELEGRAPHY. 


earth. In syntonic systems the coherer would be placed in the 
“ closed ” circuit. The position of the iron plug is adjusted by the 
screw W and rod r until the drop of mercury touches both the carbon 
and iron plugs, or until a continuous faint hissing sound is heard in 
the telephone. When oscillations occur in the coherer circuit the 
mercury coheres to the carbon and iron j when the oscillations cease 
the mercury automatically decoheres, with the result that variations 
of current sufficient to produce crackling noises in the telephone of 
long and short duration are set up during the reception of signals. 

In the practice of the Italian navy, in which the Solari coherer 
was first used, a relay is employed to operate a bell for calling. YV hen 
the telephone alone is used the operator must keep the instrument to 
his ear continuously to hear calls. It has been found by experience 
that when the tube of this coherer is not carefully closed, moisture 
enters and has a detrimental effect upon its operation. The size of 
the drop of mercury also has an important bearing on the operation 
of this coherer, and for proper working should not exceed .117 inch, 
nor be less than .058 inch, in diameter. The diameter of the tube 
should be chosen to meet these conditions. After this coherer has 
been in use for a time it loses its effectiveness, and must be renewed 
by putting in fresh mercury and thoroughly cleansing, the tube being 
easily dismounted for this purpose. 

The Marconi Magnetic Detector. —This detector of electric oscil¬ 
lations is outlined in Fig. 40. According to Marconi’s description it 

is constructed as follows: One layer 
of fine copper wire w, .007 inch 
in diameter and about 7.8 feet in 
length, is wound over a core c, made 
up of about 30 hard-drawn fine iron 
wires. The secondary wire w' of 
the same size of copper wire is wound in as many layers over w as are 
necessary to give a resistance about equal to that of the telephone t , 
which is in the circuit of the secondary wire w\ There is no battery 
in either of these wires. The inner wire w may be connected to the 
vertical wire and earth, or to the terminals of a transformer, as 
described in connection with the filings-coherer. A permanent mag¬ 
net m is placed near the end of the core c. The magnet is revolved 
by clockwork at the rate of about 30 revolutions per minute. This 
detector is based upon the observed fact, as Marconi states, that elec- 













MAGNETIC DETECTOR. 


71 


trie oscillations acting upon iron reduce the effects of magnetic hys¬ 
teresis (that property of a magnet which retards magnetic changes), 
causing the metal thereby to respond readily to any influence which 
may tend to alter its magnetic condition, as Professors Gerosa, Finzi, 
and others have pointed out. Hence, when a magnet such as core c 
is undergoing regular slow changes of magnetism, which slow mag¬ 
netization by reason of hysteresis is retarded and lags behiud the 
magnetizing force (m in this case), arriving electric oscillations in the 
wire w produce rapid changes in the magnetization of c, with the 
result that currents are set up in the coils surrounding the core, which 
currents are heard in the telephone receiver as long and short sounds 
when signals are being received. 

A modification of this arrangement consists in replacing the core c 
“ with an endless iron rope or core of thin wires revolving on pulleys 
worked by a clockwork arrangement which cause it to travel through 
the copper-wire windings, in proximity to a horseshoe magnet, or, 
preferably, two horseshoe magnets, with their poles close to the 
windings, and with their poles of the same sign adjacent. In this 
case the copper-wire windings are separated from the iron core by 
means of a stiff, thin pipe of insulating material, to prevent chafing 
of the wires. With this arrangement the signals appear to be quite 
uniform in strength.” 

Marconi further notes that this detector appears to be more sensi¬ 
tive and reliable than the filings-coherer, and does not require the careful 
adjustment and precautions which are necessary with the latter (such as 
choke coils, etc.). It will also have advantages over the filings-coherer 
when used in connection with tuned circuits in that its resistance is 
not only uniform, but is also much lower than the former when in its 
sensitive state, and “as it will work with a much lower E. M. F. the 
secondaries of the tuning transformers can be made to possess much 
less inductance, their period of oscillation being regulated by a con¬ 
denser in circuit with them, which condenser may be much larger 
(in consequence of the smaller inductance of the circuit) than is used 
for the same period of oscillation in a coherer circuit, with the result 
that the receiving circuits can be tuned much more accurately to a 
particular radiator of fairly persistent electric waves.” 

With electric detectors of the automatic type the action seems to 
be practically instantaneous, unlike the filings-coherer, in which time 
is lost in cohering and decohering. In the latter, also, decoherence 


72 


WIRELESS TELEGRAPHY. 


is not always complete, which is another drawback to its use in syn¬ 
tonic wireless telegraphy, producing as this does variations in the 
resistance of the closed circuit, which, as already noted, produces 
variations in the period of oscillation. As previously remarked, the 
speed of signaling with the filings-coherer is ten to fifteen words per 
minute. With the magnetic coherer it is claimed that a speed of 
thirty words per minute is obtainable, and Marconi has intimated that 
it will ultimately be feasible to operate this device in connection with 
automatic transmitting and receiving apparatus. 


Marconi has given interesting details of his transatlantic and 
other long-distance experiments, the first of which was between 
Poldliu and Signal Hill, Newfoundland, a distance of 2200 statute 
miles, in December of 1901. On this occasion the apparatus described 
was used at Poldhu, while a vertical wire 400 feet long, supported by a 
kite, was connected to a detector in Newfoundland. By prearrange¬ 
ment, the letter “ S” (three dots in the Morse code) was transmitted 
from Poldhu at regular intervals. This letter was heard frequently, 
but no regular message was received at that time. It was found that 
owing to the variations in the capacity of the vertical wire at Signal 
Hill, due to fluctuations of the height of the kite, the ordinary tuned 
receiver was not suitable, and therefore a number of different types 
of carbon and carbon-cobalt auto-coherers were tried and found opera¬ 
tive. These coherers were placed in the secondary wire of a trans¬ 
former, the signals being read on a telephone. The Solari auto¬ 
coherer was also used successfully on this occasion. 

In February, 1902, further experiments were made between Poldhu 
and the steamship Pliiladetyhia while on a voyage to New York. The 
receiving aerial conductor on the Philadelphia consisted of four wires 
197 feet in height above sea-level. These were attached to the mast 
of the ship, and were connected together at their lower ends to the 
/receiving instrument. In these tests the filings-coherer in a syntonic 
circuit and auto-coherers in untuned circuits were used. In these 
tests “readable messages were received on tape at a distance of 1551 
miles from Poldhu, and indications were received as far as 2099 miles, 
while signals could not be received at over 900 miles by any of the 
self-restoring coherers,” the reason for this probably lying in the fact 



MARCONI LONG-DISTANCE TESTS. 


73 


that the tuned filings-coherer “when connected to a fixed aerial con¬ 
ductor is more efficient.” 

An interesting point observed during these tests was that signals 
could be received at a greater distance at night than during the day, 
which, it was surmised, might be due to the discharging effect of 
daylight upon the highly charged aerial wires at Poldhu, it having 
been observed by Hertz during his tests that the ultra violet rays 
when allowed to fall on the discharge-knobs facilitated the discharge. 
Other experiments by Marconi also gave this same result. Thus, 
between Poldhu and Dorset, 152 miles (109 miles over sea and 43 miles 
over land), signals were received during the night with wires 39 feet 
high, while during the day wires 60 feet high were required. 

Further long-distance tests were conducted by Marconi between 
Poldhu and the Italian cruiser Carlo Alberto in July, 1902. The ver¬ 
tical conductor at Poldhu consisted of 100 thin copper wires supported 
from four towers 230 feet high; the E. M. F. employed at this station 
was practically equal to that already noted. On the Carlo Alberto , 
which was arranged a&a receiving station only, a filings-coherer and 
Morse recorder, and Marconi’s magnetic detector (see page 150) 
were employed as receivers. The vertical wires on the vessel 
were reinforced by a network of thin tinned copper wires sus¬ 
pended between the masts of the vessel. Messages were sent at pre¬ 
arranged times during the day from Poldhu. The cruiser first sailed 
for Denmark, and messages were distinctly received at a distance of 
560 miles across the North Sea and England. Subsequently messages 
were transmitted from Poldhu to the Carlo Alberto at Gibraltar and 
beyond, a distance of 750 miles. In these experiments, also, the 
distance transmissible at night was greater than during the day. It 
was also found that the effects of atmospheric electricity made it 
necessary to reduce the sensitiveness of the detectors or to provide a 
shunt for the atmospheric discharges, which doubtless has the further 
effect of diminishing the effectiveness of the received oscillations. 
These tests, it is stated, also demonstrated the superiority of the mag¬ 
netic detector over any coherer. 

In the more recent experiments a despatch has been transmitted 
from South Wellsfleet Station to Poldhu, namely, the message of con¬ 
gratulation from President Roosevelt to King Edward VII.; but up 
to the end of June, 1903, nothing further of a commercial nature 
has transpired regarding transatlantic wireless telegraphy, owing, it 


74 


WIRELESS TELEGRAPHY 


is said, to breakdowns in some parts of the apparatus. In the mean¬ 
time, however, the system which Sig. Marconi has done so much to 
develop is being installed on numbers of vessels, naval and mercan¬ 
tile, on lightships, etc. 


LETTERS. 

A 
• • 

A 

B 

C 

Ch 

D 

E 

E 

F 

Gr 

H 

I 

J 

K 

L 

M 


MORSE. 


TELEGRAPH CODES. 

CONTINENTAL.* 


LETTERS. 

N 

0 
• • 

0 
p 

Q 

R 

5 

T 

U 

• • 

U 

V 

w 

X 

Y 
Z 

6 

NUMERALS. 


MORSE. 


CONTINENTAL. 


1 

2 

3 

4 

5 


MORSE. 

CONTINENTAL. 

- - - 

- - -- 


MORSE. 


CONTINENTAL. 


6 

7 

8 
9 
0 


ABBREVIATED NUMERALS USED BY CONTINENTAL OPERATORS. 


1 ._ | 2-| 5 

7-| 8 - 


. Period 
: Colon 

; Semicolon 
, Comma 
? Interrogation 
! Exclamation 


- | 4 .... 

| 9 —- | 

PUNCTUATIONS. 

MORSE. 


— | 5 - | 6 — 
10 - (See p. 304). 

CONTINENTAL. 


* Officially termed the “ Universal ” code. 














MARCONI WIRELESS TELEGRAPH SYSTEM. 


SOME LATER DEVELOPMENTS THEREIN. 

In common with the other large commercial wireless telegraph 
companies the Marconi Company has made numerous improvements in 
its system within the past few years. Since October 17, 1907, the 
trans-Atlantic stations of this company have been in regular opera¬ 
tion, chiefly for the transmission of press dispatches, between Clifden 
, Station, Ireland, and Glace Bay Station in Cape Breton. 

These stations were designed to have a wave length of 12,000 feet 
(frequency about 82,000). The spark length employed in the original 
apparatus was from .5 to .8 inch. In the disc discharger, described in 
section on sustained oscillation generators, Part II, herein, the gap is 



Fig. i.—Marconi Magnetic Detector. Fig. 2.—Valve Detector. 

about .039 inch wide, or just sufficient to give clearance to the disc 
knobs. The use of this discharger also admits of a marked decrease 
in condenser capacity. The original condenser capacity at the Glace 
Bay station was about 1.8 microfarad; the condensers for providing 
this capacity consisting of large metal plates separated by air to avoid 
dielectric hysteresis. These plates are contained in two large build¬ 
ings in Glace Bay. 

The detectors now chiefly employed in the Marconi system are the 
Marconi magnetic, and a modification due to Marconi of the Fleming 
valve. These detectors are outlined in Figs. 1 and 2, respectively. 
In Fig. 1 , A is the aerial. I is a variable tuning coil, c is a variable 
condenser in the circuit of primary p of the magnetic detector, of 
which s is the secondary, m m' are the horseshoe magnets of the 
detector placed in proximity to the moving iron band w, with like 




















76 


WIRELESS TELEGRAPHY. 


poles together, as indicated. (See page 188.) t is a telephone receiver. 
The tuning coil l is varied in small steps as desired by means of plugs 
n n'; the use of sliding contacts not being considered advisable in 
the practice of this company, owing to defects caused by imperfect 
contacts, added to difficulties in tuning introduced, in long distance 
work especially, by the contact of the slides with more than one turn 
at a time. To meet special requirements, however, this company has 
devised a sliding contact tuner that overcomes the last mentioned 
defect. The device consists of a slider so pivoted that it jumps from 
one turn of wire to the next regardless of the direction in which it is 
being moved for tuning. 

In Fig. 2 a is the aerial. I is a variable inductance, l is the re¬ 
ceiving oscillation transformer, or jigger, c is a variable tuning con¬ 
denser. c' is a condenser of very small capacity, i is the secondary 
wire of an induction coil, in the primary of which is the telephone 
receiver t. Originally a 10-inch induction coil was used at i, but 
a smaller induction coil is now utilized. The Fleming valve detector, 
b p w, etc., is described in Chapter XIY. Marconi’s modification of 
this detector consists of the addition of the induction coil i, which in 
practice adds largely to the efficiency of the detector. 

In Fig. 3 the transmitting and receiving circuits of a 2-kilowatt 
shipboard station are outlined, omitting the usual switches, dynamo, 
field rheostats, etc. k is a telegraph key supplied with an additional 
contact c', to short circuit the telephone t and the secondary coil s of 
the magnetic detector when key k is closed. When this key is open 
the circuits are set for receiving through the secondary w of the 
oscillation transformer t', the low resistance and inductance of which 
do not materially affect arriving oscillations. A ground plate g is 
placed in the aerial circuit as shown. This plate consists of 2 flat 
cup-shaped metal discs, about l /[ inch deep, with the edges of the 
cups facing one another and about .005 inch apart. By this arrange¬ 
ment a very close and capacious spark gap is obtained, while any con¬ 
denser effect is avoided. The primary coil p of the magnetic detector 
consists of about 40 turns of fine wire, the inductance of which, to¬ 
gether with the practically direct path to ground by way of the ground 
plate g, is sufficient to ward off the high potential transmitted oscilla¬ 
tions from the said coil. By the foregoing means the need of a switch 
to alternately connect the transmitting and receiving circuits with the 
aerial is obviated. 


MARCONI CIRCUITS. 


77 


The coils of the oscillation transformer t' are wound on a frame 
12 inches long by 5 inches in width. The primary coil w consists of 
2 to 6 turns of No. 8 stranded copper wire, 4 feet to the turn. The 
secondary w' is wound over the primary, but is insulated therefrom 
by sheets of mica, and consists of 6 turns of similar wire. These 
transmitter oscillation transformers are as a rule not adjustable, the 
coils being permanently arranged for a given wave length. This ar¬ 
rangement possesses the advantage that it affords any receiving sta¬ 
tion knowing the said wave length a basis for adjustment of the re¬ 
ceiving apparatus. In some cases, however, these transformers are 
furnished with a secondary coil which may be varied from 5 to 25 
turns, 5 turns at a time. In the same figure g is the generator, s is 
the spark coil, c is the usual Leyden jar capacity of the transmitter 



Fig. 3.—2-Kilowatt Marconi Station Circuits. 


0 

•oscillation circuit, m m ' a^e the horseshoe magnets of the magnetic 
detector, the moving iron band being omitted in this figure. A 
graphite rod r is used as a protection device across the terminals of 
the primary coil of the power transformer t. These transformers are 
practically of the open core type. 

A key arrangement for 10-kilowatt stations of the Marconi com¬ 
pany is shown in Fig. 4. In this figure key k is known as the “Gray” 
key. Its particular function is to open the primary circuit of power 
transformer t at zero potential only to avoid sparking at the key con¬ 
tacts. The key has 2 levers, l V, separately pivoted as shown. Lower 
















78 


WIRELESS TELEGRAPHY. 


lever V carries an armature a of a magnet m ifl the primary circuit. 
Normally the retractile springs s s' raise up these levers. When lever 
Z is depressed it depresses lever Z', thereby closing the primary circuit 
at c'. But when the upper lever Z rises, lever V does not follow until 
the moment of no magnetism in m between two alternations. Owing, 
however, to the rapidity of the alternations in the primary circuit any 
slight tardiness of lever V in following up lever Z is not jierceptible in 
practice. 

In Fig. 3 Z, and in Fig. 4 ck ck are adjustable inductance coils to 
govern the phase displacement of the transformer. (See remarks on 



Fig. 4.—io-Kilowatt Marconi Station. Gray Key. 


resonance transformers, Chapter XI\ .) s is the spark gap. c repre¬ 
sents the usual Leyden jars in series in the oscillation circuit, t' 
is the oscillation transformer with plug contacts k, k. a is the aerial. 

In the majority of the Marconi shipboard installations 10-inch in¬ 
duction coils with hammer interrupter and storage battery are em¬ 
ployed as the source of alternating current. About one-fourth of 
these installations are also equipped with 2-kilowatt transformers 

In one of the Marconi switching keys the lever is carried on a pivot 
and an extension is provided which, in one position of the key lever, 
extends to a set of contacts connected with the transmitting circuits, at 
which time the receiving circuits are open. To close the receiving 
circuits the key must be turned on its pivot to bring its extension into 
contact with the receiving circuits. 
















CHAPTER VIII. 


LODGE AND LODGE-MUIRHEAD WIRELESS TELEGRAPH 

SYSTEMS. 

LODGE EARLY SYNTONIC WORK. 

Reference has already been made in a preceding chapter to the 
early experiments of Sir 0. Lodge in simple wireless telegraphy. As 
previously remarked, he was doubtless the first to devise syntonic, 
more especially selective syntonic, wireless telegraph methods, some of 
his British patents therefor having been issued in 1897. Lodge 
noted that the usual arrangement of the early transmitting circuit 
was calculated to produce waves of very limited duration; hence the 
effect upon the coherer is mainly due to the first swing, so to speak, 
of the oscillations. In order to obtain persistent oscillations Lodge 
first designed transmitting and receiving apparatus in which maxi¬ 



mum capacity and inductance with minimum resistance is sought, 
the transmitting and receiving circuits being constructed to have a cor¬ 
responding oscillation period, thereby securing tuning and resonance. 

This apparatus is indicated in Figs. 41, 42, in which h h are two 
triangular sheets, or capacity plates, of high-grade copper, six to eight 
feet in length (shown edgewise in figures), arranged relatively to each 
other as shown (see Fig. 43). Between the capacity plates h h are 



















80 


WIRELESS TELEGRAPHY. 


inserted one or two coils c c of a few turns of copper ribbon or wire? 
well insulated, and designed to give inductance to the circuit. To 
this end finely divided iron rods may be inserted in the coil. Polished 
metal knobs Jc' Jc' are placed on the side of each capacity plate, as 
indicated. The terminals of the secondary wire of the induction coil i 
are first brought to the inner coatings of Leyden jars j j (Pig. 41), 
the outer coatings of which are connected to the discharge-knobs n n. 
The outer coatings of the jars are connected by an induction coil i of 
thin wire to insure thorough charging of the jars, which coil provides 
an alternative path for the discharge, but does not prevent sparking 
at discharge-knobs Jc' Jc'. Between the inner coatings of the jar and 
the induction coil I there is another spark-gap and knobs b. Other 
sparking knobs V are placed at either end of the inductance coils c c. 

When the arrangement is to be used as a transmitter the knobs b' 
are separated to a suitable sparking distance. The operation is as 
follows: The induction coil I sets up charges of high potential which 
break down the air-gap resistance at the knobs Jc' Jc ', which in this 
arrangement Dr. Lodge terms the “supply ”knobs. Sparking fol¬ 
lows, and oscillations are started in the capacity sheets and induction 
coil, which, in turn, spark into each other across the knobs b' b'. 
According to the inventor, it is the latter discharge which is the 
chief agent in starting the oscillations that radiate the electric waves. 
The waves will still be radiated, however, if the air-gap at V b' be 
closed or short-circuited, but in that case the polished knobs Jc' Jc' 
must be protected from ultra violet light, for the reason stated else¬ 
where herein. The object in excluding this light is to conduce to a 
more intense rupture at the polished knobs Jc' Jc' (for which purpose 
the Leyden jars also are employed), which in turn excites stronger 
oscillations in the oscillation circuit proper, Ji Ji , c c. 

An advantage claimed at the early period mentioned (early in the 
history of this art) for this “closed” arrangement of the transmitting 
circuits, in addition to that due to the impulsive rush caused by 
charging the oscillation circuit through the supply-gaps Jc' Jc\ is that 
the said circuit has no direct metallic contact with the induction coil 
or other source of oscillations, “and therefore oscillates longer and 
more simply than when supplied by wires in the usual way.” 

When these capacity plates and inductance coils are to be used 
as a receiver, the air-gap at b' b' is closed or short-circuited, and the 
coherer circuit x x is attached to the plates near the terminals of the- 


CAPACITY PLATES. 


81 


inductance coils, as in Fig. 42, in which Tc is the coherer, b a cell of 
battery, g a galvanometer, or other receiving instrument, in series 
with the coherer. In this figure but one coil c is shown. The other 
letters in this figure refer to apparatus similarly lettered in Fig. 41. 
The tapper is not shown in these figures, which with much of the 
accompanying descriptive matter are adapted from the U. S. patent 
ho. 609,154, 1898, covering these devices. 

When it is desired to have transmitters and receivers of different 
rates of oscillations for selective signaling, Dr. Lodge employs oscil¬ 
lators with adjustable inductance coils which may readily be inserted 
between the capacity plates by means of a mercury or other suitable 
switch. By varying these coils this result is easily obtained, since 
the period of oscillation varies with the inductance as well as with 
the capacity. The plates and inductance coil of this arrangement 
can be used as transmitter and receiver by a slight change, therefore 
one set of plates is sufficient at each station. No ground connections 
or vertical wires are ordinarily used with this device, but the use of a 
ground connection is suggested. Dr. Lodge states that “radiation 
from an oscillator consisting of a pair of capacity areas is greater in 
the equatorial than in the axial direction. Consequently, when send¬ 
ing in all directions it is well to arrange the axis of the oscillator, or 
emitter, vertically. Moreover, 
with the axis thus arranged the 
emitted waves are less likely to 
be absorbed over partially con¬ 
ducting earth or water.” A 
set of oscillators arranged ver¬ 
tically for signaling to a dis¬ 
tance is shown in Fig. 43, the 
apparatus at the left represent¬ 
ing the transmitter, that at the 
right the receiver. 

Another arrangement of this 
system as outlined by the inven¬ 
tor in the patent referred to is illustrated in Fig. 44, in which c is the' 
primary and s the secondary of an ironless transformer, and c is a con¬ 
denser or resistance shunting the coherer. The object in this use of 
the transformer is to make its secondary coil “a part of the coherer 
circuit so that it shall be secondarily affected by the alternating cur- 



























82 


WIRELESS TELEGRAPHY. 


rents excited in the conductor of the resonator, and thus the coherer 
be stimulated by the currents in this secondary rather than primarily 
by the currents in the syntonizing coil itself; the idea being thus to 
leave the resonator freer to vibrate electrically without disturbance 
from attached wires”—in other words, to provide a “closed” circuit 
as distinguished from the ‘ ‘ open ” circuit. 




In a subsequent British patent, No. 18,644, 1897, to Lodge and 
Muirhead, a condenser is described as shunting the receiving instru¬ 
ment and battery, virtually as outlined in Fig. 45, and this is referred 
to as a distinct part of the invention, allowing as it does the coherer 
circuit to have a definite period of oscillation, and practically elimi¬ 
nating the said battery and receiving instrument so far as oscilla¬ 
tions are concerned. Fig. 45 is not, however, taken from said patent. 

Signals are said to have been received at a distance of one mile by 
the apparatus and system described. How much farther it may be 
capable of transmitting signals is not known to the writer. 

Further allusion is made to Fig. 45 as representing a “closed” 
receiving circuit (p. 82). In the figure c' is a condenser, indicated 
as shunting a siphon recorder a , and battery Z>; h is a coherer; c is a 
condenser and p is the primary of a transformer, both in the aerial 
circuit; s is the secondary of the transformer. 


Lodge-Muirhead Single-Point Coherers.—One of the coherers 
used by Dr. Lodge, and known as a single-point coherer, consists of 
a suitably supported metal point resting easily on a light metal rod. 
The rod and the point are connected as in the case of the ordinary 
coherer. When electric waves occur the point slightly coheres to the 
















LODGE-MUIRHEAD FILINGS-COHERER. 


83 


rod, thereby reducing the resistance of the circuit. The rod is main¬ 
tained in a very slight state of tremor by means of a rotating wheel 
at its left end, which wheel is rotated by clockwork. This suffices 
to decohere the point, the effect being virtually similar to that of the 
filings-coherer upon the circuit. 

A modification of this coherer is described in the patent last men¬ 
tioned, and is outlined in Fig. 46, in which c c c are strips of metal 
resting lightly against contact-points indicated by the arrow-heads. 
Under the influence of electric oscillations in the circuit the points c 
cohere. These points, it will be seen, are in multiple with each other 
and in series with the receiving instrument «, a siphon recorder. 
Two or more points are used to insure that action will ensue. The 
coherers are in mechanical contact with a rotating cam d which at 
each revolution decoheres the points. 




Fig. 47 . Muirhead Filings-Coherer. 


Lodge-Muirhead Filings-Coherer.—These inventors have also 
devised a means of decohering filings without the aid of vibrating 
hammers or similar apparatus. The filings c, Fig. 47, are spread on 
a flexible light strip / which is suitably supported at its right end 
only, and is placed in the magnetic field of a permanent or electro¬ 
magnet N s. The filings are separated from the strip by a film of 
varnish or other suitable insulating material, excepting for a short 
space at the left, as shown, where the filings rest on the strip. 
Another light metal strip t is held by small springs g g against the 
filings. When the filings cohere a current from the cell b flows 
through the strip, and by the joint action of the magnetic field and 
the field due to the current the strip is deflected, and in consequence 
the mass of the filings is disturbed and decoheres. 






















84 


WIRELESS TELEGRAPHY. 


LODGE-MUIRHEAD WIRELESS TELEGRAPH SYSTEM. 


More recently these gentlemen have put on the market a com¬ 
pleted commercial system intended for signaling over short distances, 
say up to sixty or eighty miles, and for this purpose it is claimed to be- 
superior to any previous system as regards reliability and clearness 
of signaling. 

One of the objects of the inventors has been to follow as closely as 
practicable upon the established methods of wire telegraphy so far as 
regards the actual transmission and reception of signals. To this end 

they provide a manually operated key, and 
also a perforator and automatic transmitter 
for sending, and a siphon recorder operated 
by a coherer for receiving. For moderate 
distances a ten-inch spark induction coil is 
used, but for long distances an alternating- 
current generator is employed. The induc¬ 
tion coil is provided with a spark-gap carried 
on an insulated frame, apart from the coil, as 
in Fig. 48, in which f is the frame, s is the 
air-gap, and R r' represent lower and upper 
rods connected with the secondary terminals of the induction coil 
by suitable insulated wires. The upper rod is adjustable by means 
of a set-screw. 

A somewhat novel interrupter for the induction coil consists of 
an arrangement whereby, whether the signaling is by hand or auto¬ 
matically, the primary of the induction coil is opened and closed at a 
definite rate by a device consisting of two telegraphic sounders so con¬ 
nected as to act reciprocally, and operated by a Morse key or an auto¬ 
matic transmitter. One of these sounders controls a lever, from one 
end of which an aluminum arm terminating in a copper rod extends 
into a cup of mercury. This arrangement acts as a “ buzzer ,” 
making and breaking the primary circuit at the rate of about ten times 
per second while the key is depressed. This apparatus is adjusted to* 
meet best conditions by varying the play of the armatures or by vary¬ 
ing the length of the dip of the arm in mercury. The record, it will 
be understood is made in consecutive dots and dashes in this svs- 



Fig. 48. 


* See article by H. C. Marillier, “ London Electrician,” Mar. 27,1903. 


OIL-FILM COHERER. 


85 


tern, not in characters corresponding to those made by the siphon 
recorder in cable telegraphy—the record or line on one side of a zero- 
line representing a dot, that on the other side a dash. It is found 
that when the rate of sparking is not sufficient the line produced by 
the recorder on the tape is uneven, while at a higher rate the pen is- 
held over during the continuance of a dot or dash, thus giving even 
lines. It has also been found, however, that with the latest type of 
coherer employed in this system the siphon recorder indicates on the 
tape every variation in the form of the transmitted wave and is thus 
useful in providing a means of studying the variations in the modes 
of signaling. At the same time these inequalities in the lines on the 
paper tape do not affect the ability of the operator to translate the- 
recorded signals. 

When the system is arranged for ordinary open-circuit, or untuned, 
working, the aerial conductor consists of an elevated capacity, such 
as a globe or roof or an iron cage from which the vertical wire is 
suspended, and connections are made to the sparking knobs and to- 
the ground in the usual way. 



One of the most important features of this system is the new type- 
of coherer employed. In practice it is inclosed in an iron case, and is 
shown in section in Fig. 49 and in top view in Fig. 50. In Fig. 49, 
w is a rotating steel disk, the periphery of which enters a vessel r 
containing mercury m, but is prevented from making contact with 
the mercury by a film of mineral oil; s is a spiral of amalgamated 
platinum wire, which insures connection between the mercury and the 
terminal-screw Z>; s' is a flat spring carrying at its right end a small 
piece of felt, which, resting lightly on the periphery of the disk w, 
keeps it free of dust. The disk w is rotated by clockwork, to which 






































86 


WIRELESS TELEGRAPHY 


it is geared by ebonite wheels h on axle a , Fig. 50. The coherer cir¬ 
cuit is completed by wires connected to the terminal-screw b and to 
the upper brush c , which rests on the axle of the disk. The film of oil 
normally prevents contact between the disk w and the mercury m, 
but electric oscillations in the circuit cause the mercury and disk to 
cohere. By means of a potentiometer ( p , Fig. 51) the normal voltage 
of the coherer circuit is maintained at from .03 to .5 volt; one volt 
being sufficient when the disk is rotating at a moderate speed to break 
down the normal insulation of the coherer and to bring about coherence. 

A later arrangement of this system is shown in Fig. 51. D is an 
alternating-current generator; A, an ammeter; v, a voltmeter; sw, 
switch to disconnect receiving system; e, fuse; SF, safety fuse; 
ac, adjustable choking coils; k, Morse key; T, sending transformer; 
ms, multiple spark-gap, shunted with small capacities, c', whereby 
high potentials-and short gaps without arcs are obtained; rt is 
the receiving transformer; y?, potentiometer to regulate voltage of 
battery b in the local circuit. The antenna is not grounded. It con¬ 
sists of a network of wire an with an area of 6400 square feet, upheld 



Fig. 51. 


by four masts eighty feet high and eighty feet apart. At the foot of 
the masts there is a similar network cp, termed a counterpoise, 
upheld by porcelain insulators at a height of three feet from the 
ground and carefully insulated therefrom. The inductance i is used 
to compensate for the inductance s in receiving transformer; or to 
effect a balance between the upper and lower network systems. The 
apparatus at each station is tuned to similar wave-lengths, namely, 
1500 feet, by means of an adjustable inductance or capacity. Con¬ 
denser c has large capacity relative to the coherer &, whereby varia¬ 
tions of the capacity of the latter do not disturb the resonance of the 
receiving circuit. Condenser c' shunting the recorder is employed 
to avoid any effect of the magnetic discharge o* the siphon recorder 
SR upon the coherer. 






















CHAPTER IX. 


THE SLABY-AECO AND BEAUN WIEELESS TELEGEAPH 

SYSTEMS. 

THE SLABY-ARCO SYNTONIC WIRELESS TELEGRAPH SYSTEM. 

According to Dr. Slaby, this system is based on the principle 
that when electric oscillations of high frequency and high potential 
are set up in a conductor, one end of which is free and the other end 
to earth, the greatest amplitude of oscillation will be at the free end 
of the wire; and, further, when electric waves are radiated from such 
a transmitting wire and fall upon a similar receiving wire, the great¬ 
est amplitude of the oscillations will also occur at the free end of 
that wire—it being assumed in each case that the wire is one quarter 
the wave-length of the transmitted wave. From this it follows that 
the coherer should be attached to the free or upper end of the receiv¬ 
ing wire, but as this is not convenient, Slaby-Arco attach a horizontal 
wire to the foot or nodal point of the receiving wire. This horizontal 
wire takes up corresponding oscillations to those of the vertical wire. 
The wires are given equal inductance and capacity, to secure syntony. 

In illustration of the foregoing theory, Dr. Slaby gives the follow¬ 
ing mechanical analogy: Deferring to Fig. 52, a b, 2 3 4 is a steel 
wire so bent that the upright ends 


cu\ 

/, 


77 ?*“ 


3 

Fig. 52. 


& 


l 

jr 


a b are each one sixth the length 
of the whole wire. When one of 
the free ends, say a , is caused to 
oscillate, the other end b likewise 
begins to oscillate. The nodes of 

the oscillation are at 1, 3, 5, while at 2, 4 and the upper end of a b 
the oscillation is a maximum. In the experiment the length of a b 
must be one quarter of the whole wave-length, or equal to the dis¬ 
tance from 1 to 2. The length of a then corresponds to the trans- 








88 


WIRELESS TELEGRAPHY. 


mitting vertical wire, connected to earth through the spark-gap, while 
b corresponds to the receiving vertical wire, the lower end of which is 
grounded and hence is a node of the electric oscillations. 

The manner in which this theory is carried out in practice is 
shown theoretically in Figs. 53, 54, which represent the transmitting 
and receiving apparatus of this system. a is the vertical wire 
terminating directly in the earth; the horizontal wire is connected 
to the nodal point of a; i is the oscillator; c is an adjustable con¬ 
denser or battery of Leyden jars; m is an adjustable inductance coil. 



The aerial wire is looped into the operating-room. A coil of wire w' 
is inserted in the vertical wire for the usual purpose, namely, to 
increase the wave-length. A set of these coils, of different induct¬ 
ances, is provided in order that any desired wave-lengths may be 
obtained. Dr. Slaby, in common with others, finds it very necessary 
that the oscillator circuit be tuned in harmony with the vertical 
wire, which may readily be done by means of the adjustable coil m 
or the capacities c, which are suitably marked for the purpose. 

In the receiving circuits (Fig. 54) a is the aerial wire, w is the 
horizontal wire connected to A. This wire may be wound on a spool 
in order to be accessible, and the coherer k is connected as indicated. 
Dr. Slaby states that the pressure, which is at its maximum at the 
end of w, is intensified by the tuning coil or multiplier m\ which 
is in the coherer circuit. R is a polarized relay in the coherer cir¬ 
cuit. Its resistance is 2000 ohms, which is also the resistance of the 
coherer when cohered, c is a mica condenser having a capacity of 
.01 microfarad, and shunting the battery b of one dry cell and relay R, 
thereby preventing the inductance effects of the relay upon the 













TUNING METHOD. 


89 


^coherer. It also gives the oscillations a free path to earth. The 
capacity of the coherer is .001 microfarad. 

The multiplier m' is a loosely wound coil of wire of a form and 
winding so proportioned that with the condenser c and inductance w 
a large increase of potential is resonantly obtained at its free end, to 
which the coherer is attached. This coil and w may be combined in 
a single coil with corresponding winding. When this coil is attached 
to the aerial wire for transmitting it imparts to that wire a higher 
potential than is obtainable by means of the induction coil alone. 

Professor Slaby gives the following method of tuning by this sys¬ 
tem: Any two stations use a prearranged wave-length. Waves of this 
length are then the only ones that affect the coherer circuit, the other 
waves passing into the earth. When, however, it is desired to receive 
at this station with the same aerial wire waves of other lengths, it can 
readily be done. For instance, if the vertical wire he 120 feet in 
length the wave-length will be 480 feet, and if the horizontal wire is 
of the same dimensions it will reject all other wave-lengths, as stated. 
But if the whole length of the vertical wire and the horizontal wire 
•combined is made equal to one half of the wave-length, the received 
waves will then be forced into the coherer circuit, for the earthed 
point is then no longer a node, but will only permit this special wave¬ 
length to enter. If it is desired to receive waves 600 feet long, the 
whole wire must be 300 feet, and the horizontal wire w, which is wound 
on a spool, must be 180 feet long. To facilitate the reception of 
signals of different wave-lengths, therefore, at any station, it is only 
necessary to provide a number of such spools capable of being readily 
attached to the lower end of the vertical wire, each of which coils is 
connected with a receiving apparatus. 

Ordinarily, two vertical wires, joined at the top, with the usual 
spark-gap, shunted by a condenser, in series in the loop thus formed, 
will not act as a radiator, or at best very feebly, since the waves tend¬ 
ing to be set up in one wire are neutralized by those in the other. 
Prof. Slaby has found that by giving one of the wires more inductance 
than the other, and by earthing the wire having the greater induct¬ 
ance, he obtains a looped system capable of radiating electric waves. 
This result is due to the fact that overtones, say the first odd har¬ 
monic, of the original oscillations are set up which produce nodes of 
potential at the bottom, and one third from the top, and an anti-node 
.of potential at the top. 


90 


WIRELESS TELEGRAPHY. 



The Slaby-Arco Coherer. —The coherer k consists of silver or plati¬ 
num and steel filings, the tube being exhausted of air to prevent 
oxidizing and to keep the filings dry and easily movable. The filings 
are decohered by a tapper. The coherer plugs are of silver, and fit 
the glass tube closely to prevent the powder from getting between the 
plugs and the glass. The leading-in wires are of platinum, and are 
fastened by metal caps to the ends of the tube. The inner ends of 
the coherer plugs are inclined so that the space or slit between them is 
wedge-shaped. The object of this device is to secure greater or less 
sensitiveness of the coherer, as desired. When the tube is so turned 
that the wider portion of the slit is below, the powder is spread over 
a large surface, and in consequence the pressure is loosened and the 
coherer is then at its point of least sensitiveness. When, on the other 
hand, the slit is turned with its narrow portion down, the filings are 
crowded together and the sensitiveness of the coherer is at a maxi¬ 
mum.- As means are provided for turning the coherer on its axis, its 
sensitiveness is thus readily adjustable. When the desired adjust¬ 
ment is obtained the coherer is locked in that position by a catch¬ 
spring. In practice these 
coherers are made in various 
degrees of sensitiveness, and 
when one becomes defective, 
or a change for any reason is 
desired, it is easily removed 
from its support. 

The Polarized Relay.—- 
There are numerous different 
forms of polarized relays in 
use in wireless telegraphy, 
but the general principle, a 
brief description of which 
will be given, is the same in 
all, and is practically as fol¬ 
lows : The form shown in 
Fig. 55 is known as the 
Phelps relay, which was at one time in extensive use in the United 
States, but has been supplanted by forms in which the moving parts 
are lighter and the instrument generally is much more sensitive. The 
polarized relay is usually a combination of a permanent magnet and 




THE POLARIZED RELAY. 


91 


ilectromagnet. In the type illustrated in the figure the permanent 
magnet pm, bent to the shape shown, rests on the base of the instru¬ 
ment. The yoke or cross-piece of the electromagnet rests on the 
lower end or south pole sp of the permanent magnet. A soft-iron 
armature a is pivoted to the upper part or north pole np of pm at x, and 
extends between the pole-faces of em. This armature is constantly 
magnetized by the permanent magnet, as are also the iron cores of the 
electromagnets, the outer end of the former to north polarity, the 
latter to south polarity, so that normally, when the armature is 
“centered/’ it will remain against either stop c c', inasmuch as it is 
attracted equally by both poles. When, however, a current traverses 
the coils of the relay, the magnetism of the cores, due to the perma¬ 
nent magnet, is overcome or assisted, and the poles of em become 
north or south poles according to the direction of the current in the 
coils, and the armature is attracted to the south pole. The play of 
the armature is adjusted by means of the small screw s'. Its position 
between the cores of the electromagnet is regulated by the front and 
back stops, one of which is the contact-point, the other being insu¬ 
lated or idle. These contacts ride in a carriage which is movable in 
the cylinder r by the screw H, and the armature may be placed in 
any position between the poles of em by this screw. The cores of 
the relay may be independently moved to and from the armature by 
the screws n n'. If no retractile spring is used, the armature is given 
a slight bias by means of the adjusting-screw H sufficient to hold it 
normally against the insulated stop; a current in the coils then moves 
the armature against the contact-point, thereby operating a sounder, 
bell, or ink-recorder. In certain other types of polarized relays the 
armature or the cores only are polarized by the permanent magnet. 


The Slaby-Arco system is designed for transmitting over distances 
ranging from 25 to 50 miles and more, over sea. For short distances 
a 6-inch spark induction coil is used with the ordinary interrupter. 
The primary battery consists of dry cells with an E. M. F. of about 
15 volts and 3 to 6 amperes. For a distance of from 25 to 50 miles 
a more powerful induction coil, with a mercury turbine interrupter, 
which is driven by an electric motor, is employed (Fig. 57). In this 
case there are about 20 interruptions per second, and the E. M. F. 
and current strength of the primary current are 65 volts and 15 



WIRELESS TELEGRAPHY. 


92 


amperes respectively. For distances over 50 miles an alternating* 
current generator of 3 kilowatts or more is used. 

The transmitting apparatus for medium distances is shown in 



Fig. 56 . Slaby-Arco Transmitting Circuits. Fig. 57 . 


some detail in Fig. 56, in which the arrangement of circuits may be 
considered as practically similar to those of the theoretical diagram 

(Fig. 53). c is a battery of 3, 7, or 14 Ley¬ 
den jars contained in the cylindrical box b; 
m is a tuning coil of about 4 turns of No. 12 
wire wound around the micanite box b; I is 
the induction coil, s the spark-gap, w tv' the 
coils already referred to, and a is the ver¬ 
tical wire. 

Fig. 57 represents the primary circuit 
connections of the oscillator, i is the induc¬ 
tion coil; K is the transmitting key; c' is a 
condenser shunting the mercury interrupter 
M, operated by the motor m ; s is a resistance 
with a sliding contact to regulate the speed 
of the motor, and by this means any num¬ 
ber of interruptions from 10 to 10,000 per 
minute can be obtained; R is a resistance 
for regulating the current strength in the 
primary of i; x is a lightning arrester; r> is 
Fig. 58. the source 0 f j]. M. F. 

The high-tension discharge-rods s are arranged vertically on the 
top of a cylinder B of micanite or other insulating material, Fig. 58. 






















































































SHIPBOARD OUTFITS. 


93 


The sparking-rods are inclosed in a micanite case to deaden the sound, 
.and for ventilation an ebonite tube is provided. To minimize acci¬ 
dents the high-tension poles are painted red. 

The usual tapper, signaling bell, and Morse ink-recorder are em¬ 
ployed in this system, but these, with numerous other necessary 
practical details, are omitted to simplify the diagrams. 

The Slaby-Arco system is exploited by the General Electric Com¬ 
pany of Berlin, from whose publications on the subject a portion of 
this subject-matter is extracted. By this system signals have been 
transmitted over sea 60 miles with masts 164 feet high, and it is 
claimed that by means of the tuning devices employed the transmitter 
and receiver can be attuned to within three per cent, of exact syntony. 
It is also claimed that a radiation equal to that of other systems can 
be obtained by this apparatus with one half the electrical energy 
required by other wireless systems. 

For portable outfits for military and similar purposes much sim¬ 
pler apparatus than that described is furnished. Kites or balloons 
in this case are utilized to support the aerial wire. Oscillations are 
set up by a Ruhmkorff coil. The Morse relay and ink-recorder are 
replaced by a head telephone receiver, and in place of the filings- 
coherer an auto-coherer placed in the secondary of a small trans¬ 
former or branch circuit is employed. The coherer is in series with 
a dry cell and the telephone receiver. The received oscillations cause 
fluctuations in the current which are heard in the telephone. A fre¬ 
quency of at least 100 sparks per second in the transmitter is found 
essential to give audible signals in the telephone. The circuits are 
attuned to the wave-length emitted by the transmitter. 

The following details of installations of this system on shipboard, 
lighthouses, etc., have been published by Count Arco, coinventor 
with Prof. Slaby of this system. 

The outfit on the s. s. Deutschland is allotted a space of about 
3 x 4.5 feet and 7 feet high. The oscillations are set up by an induc¬ 
tion coil giving a 20-inch spark,'supplied with alternating current of 
5 to 20 amperes with a frequency of 25, thereby avoiding the need of 
an interrupter. The transmitting key is supplied with an electro¬ 
magnetic blow-out, so that no sparking occurs at 'the break. To 
cOiirponsate as far as possible for the rolling and pitehihg of the ves¬ 
sel, all movable parts, such as the relay armatures, are'counterbalanced, 
and to diminish the vibration, which is most noticeable at half-Speed 


94 


WIRELESS TELEGRAPHY. 


of the ship, felt and rubber packing is employed; but despite these 
precautions these causes reduce considerably the sensitiveness of the 
apparatus. The vertical conductor consists of a cable of twelve wires. 
This cable is not a permanent structure, but is raised to the mizzen¬ 
mast when required. The transmitting wire is insulated with india- 
rubber, .4 inch thick, to prevent contact with the deck. 

Arrangements are provided to make it feasible to communicate 
with stations and vessels equipped with other systems than the Slaby- 
Arco. The quarter wave-length employed at Duhnen, Germany, is 
about 300 feet; that at Heligoland is about 150 feet. For the pur¬ 
pose stated a switch is provided on the Deutschland whereby the 
properly attuned coils may be switched in for the stations at Duhnen 
and at Nantucket lightship. The maximum distance at which com¬ 
munication has been made between the said vessel and Nantucket is 
about 50 miles, while from the ship to Duhnen a distance of 100 
miles has been covered. It is assumed the ship’s tackle intercepts 
the waves in the first instance. For communication between the 
lightship Vyl and the Blaavandshuk lighthouse off Denmark, a dis¬ 
tance of about 19 miles, it was necessary to take into consideration 
the heavy rolling and pitching of the lightship in stormy weather. 
At this station an induction coil giving a 2-inch spark is operated by 
large dry cells which supply 2.5 amperes at 10 volts, and owing to 
the small energy available a condenser having a capacity of but 
.0005 microfarad can be employed. 

No mast is employed at the lighthouse. A wire about 208 feet 
long is dropped from the lantern to a hut nearby, giving a vertical 
height of about 160 feet. Current in the lighthouse is furnished by 
a storage battery giving 20 amperes and 40 volts, the battery behig 
charged once in two weeks. Inasmuch as the vertical wires at these 
two stations are of different lengths, the following plan is adopted to 
obtain syntony. When signals are being transmitted by the lightship 
both air-wires are tuned to the same frequency, at which time the ver¬ 
tical wire of the former oscillates in quarter waves and that of the 
lighthouse in three-quarter waves. Reversely, when the lighthouse 
is transmitting, both air-wires oscillate at a uniform rate, namely, in 
quarter waves, the fundamental rate of oscillation of the lightship 
being reduced by the insertion of a large inductance coil in its circuit. 

Further advantages claimed for this system by the inventors a?e 
the entire absence of atmospheric disturbances during the reception 


BRAUN SYNTONIC SYSTEM. 


95 


of signals; the possibility of using for the aerial wire, for transmitting 
and receiving, lightning-conductors, iron chimneys, or other similar 
earth conductors; and the possibility of receiving without interference 
messages from several transmitting stations, owing to the great inten¬ 
sity of the syntonizer employed. 


THE BRAUN SYNTONIC WIRELESS TELEGRAPH SYSTEM. 

This system, due to Prof. F. Braun, known also as the Braun- 
Siemens-Halske system, is established in a number of places in Europe. 

The important features of the Braun system are closed transmit¬ 
ting and receiving circuits and the use of large capacity areas instead 
of earth connections at the base of the aerial wire. By the closed- 
circuit feature it is well known that more persistent oscillations are 
obtainable, and by avoiding direct earth connections atmospheric elec¬ 
tric disturbances are obviated. 

The theory of the Braun transmitting and receiving circuits is 
outlined in Figs. 59 and 60. In Fig. 59, 5 is the battery or E. M. F. 




Theory of Braun Syntonic System. 

for the operation of the usual induction coil I, the interruptions of 
the primary circuit of which are made by a mercury circuit-breaker, 
or a Wehnelt interrupter, not shown in this figure; which interruptions 
are broken into Morse dots and dashes by a heavily constructed key K. 
A primary wire p of a spirally-wound inductance coil, termed an 
inductor, T, Leyden jars c c, and the spark-gap s, form the closed 
transmitting oscillation circuit. The oscillations set up by the induc¬ 
tion coil i are transformed up in the secondary wire s, one end of which 
is connected to the aerial wire a, the other end to a capacity consist- 















WIRELESS TELEGRAPHY. 


96 

ing of a large metal plate or cylinders K, or the terminal may be- 
coiled up loosely to avoid inductance. There is thus here the closed 
oscillating circuit to produce persistent high-frequency oscillations 
combined with the open circuit, consisting of k and the aerial wire a, 
which is a powerful radiator, and which thus radiates strongly the 
persistent oscillations which have been transformed to a higher poten¬ 
tial by transformer T. The aerial wire and k are so chosen as to 
be each one fourth of the emitted wave-length, as indicated by the 

symbol —; the frequency and consequently the wave-length of oscilla¬ 
tions depending on the resistance, inductance, and capacity of the- 
respective circuits, according to the formula given (see pp. 21, 50). 

Concerning these features of his system Professor Braun remarks 
as follows: The condenser discharges through a primary circuit which 
excites the lower spirally-wound end of the transmitter, which remains 
insulated from the earth. Hence it follows that the function of the 
earth in increasing the transmitting distance cannot be explained in 
the usual manner; possibly the earth causes the transmitter to take 
up greater electromagnetic energy. Also in the primary circuit a 
large amount of energy can be employed usefully, and the action of 
the transmitter increases with the energy employed to a much greater- 
extent than when the direct earth connection is employed. Further, 
the action of the transmitter can be augmented by increasing the 
capacity of the condensers as well as by an increase of potential. 
Again, the oscillations of the primary circuit are but slightly damped, 
and thus excite in the open circuit oscillations which are still less 
damped. He gives the following examples of the relative electro¬ 
magnetic energy in the transmitter when directly excited, and when 
inductively excited, as by his method. With 2 amperes in the pri¬ 
mary circuit the electromagnetic energy for direct excitation is 8; 
for inductive excitation, 26. With 6 amperes in the primary circuit 
the electromagnetic energy for direct excitation is 10; for inductive 
excitation, 62. 

In Fig. 60, representing the receiving circuits, it will be seen 
that the arrangement of the transmitting apparatus is virtually re¬ 
versed, the aerial wire A and K being the primary circuit, the weak 
received oscillations being transferred to the closed circuit j) s' c' c\ 
where in turn they are transformed to higher potential by the secondary 
$ of transformer t' to the circuit of coherer 7c, which controls relay r 


BRAUN UNTUNED SYSTEM. 


9? 


(operated b) T a cell It) in the usual way. These respective circuits are 
also arranged as indicated, to have one quarter the length of the 
received wave, the closed circuit d s' dp being tuned to the transmit¬ 
ting circuit, or to some multiple of that circuit, by means of the 
transformer, thereby “bringing about resonance in that circuit anal¬ 
ogous to that obtained in acoustics/’ Inasmuch as the received oscil¬ 
lations are much weaker than those emitted, the size of the conden¬ 
sers d d and transformer t' is much less than those of the transmit¬ 
ting system, and are contained in small closed cases. The condensers 
are of the mica type and non-adjustable. 

In the case of untuned circuits Professor Braun arranges the 
receiving system as outlined in Figs. 61 and 62. In the former the 


Fig. 61. Fig. 62. 

Theory of Braun Untuned System. 

transformer t' is not used, and terminal 1 of coherer tc is connected to 
the right end of the closed oscillator circuit as shown, its other ter¬ 
minal 2 being connected to a large capacity plate k'. In Fig. 62 
terminal 1 of the coherer is connected to 6*', while terminal 2 is con¬ 
nected to the secondary of the transformer t'. In these cases, of 
course, resonance is not sought. 

The form of condensers adopted by 
Professor Braun for the transmitter is 
that of the miniature Leyden-jar arrange¬ 
ment shown separately in Fig. 63. This 
cylindrical form is chosen for compact¬ 
ness and ease of adjustment. Each cylin¬ 
der consists of two tubes sliding one 
within the other. The tubes are of glass 
.078 inch thick, and have a diameter of 
about 1 inch. They are interchangeable 
within the limits of .19 inch and .008 inch, 
in steps of .08 inch. The cylinders vary in capacity from .0004 to 
.0005 microfarad, and thus with the sliding feature facilitate pro¬ 
curing either minute or comparatively wide variations in the fre- 
































































































98 


J 


WIRELESS TELEGRAPHY. 


quency of the oscillations. The tubes are easily replaced when broken, 
or when necessary for other purposes, since it is only necessary to 
insert them in the appropriate rack to put them in service, suitable 
contact arrangements being provided therefor. 

The spark-balls s are contained in a glass cylinder carried on the 
base of the Leyden-jar racks, as shown in Fig. 63. The cylinder has 
ebonite ends and is filled with oil, to obtain a higher inductive capac¬ 
ity than that of air. 

The high-tension transformer or induction coil T of the transmit¬ 
ting system is depicted in Fig. 64. As this coil carries heavy currents, 

it is constructed accordingly. Its pri¬ 
mary has four turns of heavy wire. The 
secondary consists of forty turns of com¬ 
paratively large wire wound outside of 
the primary. This induction coil is not 
specially wound to give high electro¬ 
motive force, but is designed to have 
low inductance and a small time con¬ 
stant, and also bv reason of low induct- 
ance to admit of the use of comparatively 
large capacity in the circuit, thereby per¬ 
mitting more accurate tuning (see p. 71). 
The large wire used also tends to low resistance and therefore small 
heat losses. When in use the coil is immersed in oil. All the features 
of this coil or inductor are carefully designed to conform to the wave¬ 
length that may be chosen, which, in order to obtain best results, should 
be four times that of the length of the vertical wire. The primary wire 
is utilized to supply inductance for the closed circuit, the desired tuning 
of which is secured by varying the capacity of the adjustable Leyden 
jars and the resistance of the spark-gap, the latter by increasing or 
decreasing its length. I he secondary wire is also adjusted in har- 
mony with the oscillations of the aerial wire. In other words, the 
diffeient ciicuits by these means are brought into the required 
attunement necessary for best results. 



Fig. 64. 

The Braun Inductor. 


The circuits and apparatus of the Braun system are shown dia- 
grammatically in Fig. 65, the transmitting apparatus at the left, the 
receiving apparatus at the right. I is the induction coil; w is a 
Wehnelt or other electrolytic interrupter, described in the section on 














BRAUN CIRCUITS AND APPARATUS. 


99 


interrupters. The Morse key k' is in the primary circuit of induc¬ 
tion coil i. b is the source of E. M. F., which should be from 40 to 
80 volts when an electrolytic interrupter is employed. When this 
voltage is not obtainable a turbine mercury interrupter is utilized, 
s is the spark-gap; c c are the Leyden-jar capacities of Fig. 63; t is 



Fig. 65. 

The Braun Transmitting and Receiving Apparatus and Circuits. 


the inductor (Fig. 64), of which p and s are the primary and secondary 
wires. One terminal of s leads to k, which is a capacity in the shape 
of a large metal cylinder about two feet long, used in place of the 
earth. The other terminal leads to a contact of the large double¬ 
throw knife-switch s'. The aerial wire comes to the middle contact 
of the switch. By means of this switch the aerial wire A may be put in 
connection with the receiving or transmitting circuits at will. In the 
figure the vertical wire is connected with the receiving system. From 
the upper right-hand contact of s' a wire leads to the closed receiving 
circuit c r p r\ thence to another cylindrical capacity k'. One ter¬ 
minal of the secondary s of t' is connected to the coherer ic\ the 
other terminal is coiled up loosely as at w. R is a Siemens polarized 
relay inclosed in a suitable case to exclude dust, and is adjustable 
from the outside of the case, as indicated in Fig. 68. A dry cell b 
is in series with the relay, and both are in circuit with the coherer. 
The polarized relay operates an ink-recorder r'. In practice the 
coherer connections are somewhat different to those shown in the 
figure, two wires leading from its terminals to contact parts on the 
switch s', so arranged that when the switch is thrown to the left the 
coherer circuit is entirely disconnected from the rest of the apparatus. 


































































100 


WIRELESS TELEGRAPHY. 


A filings-coherer shown in Figs. 66 and 67 is used in this system. 
The filings are of hardened and sieved, powdered steel contained in an 
inner ebonite tube within the tube k. The tube is not exhausted, 



Fig. 66. The Braun Coherer. Fig. 67. 


Professor Braun’s experiments having shown that the vacuum coherer 
is not more sensitive and is far less easy of adjustment than the non- 
exhausted type. The leading-in rods r r' are of polished steel. The 
rod r is held in the tube by the set-screw s. Rod r is adjustable to 
or from the filings by the adjusting-screw s', the spiral spring a with¬ 
drawing the plug when s' is screwed outwardly. When the desired 
adjustment is secured the screw s' is locked by a jam-nut. The com¬ 
pleted coherer is supported in its proper position by two metal posts, 
on the upper end of which are clutches forming the contacts leading 
to the relay and receiver transformer circuits, and into and out of 
which clutches the coherer may be quickly inserted or removed. 

The sensitiveness of the coherer is increased by the use of coarser 
filings. Inasmuch as it has been found that a certain degree of mag¬ 
netism in the conductor plugs adds to the sensitiveness of the coherer 
without impairing its reliability, a magnetic ring is placed over the 
tube and between the ends of the plugs. By turning this ring so 
that its magnetic poles approach the plugs at the proper distance the 
required degree of magnetization of the plugs is obtained. Instead 
of the electro-mechanical tapper so commonly employed, a tapper 
operated by clockwork is employed for decohering the filings in this 
system. An advantage of the spring tapper is that the blows are 
always struck with the same force, hence restoring the filings to the 
same -position at each stroke. When the filings have cohered an 



















BRAUN KEY. 


101 


electrically operated spring clutch releases the tapper, and when the- 
filings decohere the clutch automatically holds the tapper. An auto- 
coherer of the carbon type is utilized in connection with a tele¬ 
phone receiver when for any reason the filings-coherer is temporarily 
inoperative. 

The Braun-Morse key is shown in Fig. 68. This key is capable 
of breaking a current of 50 amperes continuously without injury to 
the interrupter. To effect this result the 
primary circuit is by a suitable device closed 
and opened separately from the main con¬ 
tact, and hence there is no sparking at the 
main contact. The key proper is mounted 
in a box within which the opening of circuit 
occurs, and a magnetic blow-out is provided 
to diminish sparking. The sides of the box 
are perforated for ventilation. 

The military outfit of the Braun system 
is carried on two carts, one of which holds 
the apparatus, the other a gasoline motor. Balloons or kites may be 
employed to sustain the vertical wire. A number of these outfits 
have been supplied to the United States government as well as to a 
number of European governments. 



Fig. 68. 





















THE TELEFUNKEN WIRELESS—RAILWAY WIRELESS- 

SINGING SPARK—VON LEPEL WIRELESS TELE¬ 
GRAPH—TELEFUNKEN, UNITED STATES SIGNAL 

CORPS, CLARK PORTABLE OUTFITS—ETC. 

TELEFUNKEN WIRELESS TELEGRAPH. 

The Slaby-Arco and the Braun wireless systems are now and for 
some time past have been consolidated under the name of the Tele- 
funken (Far Spark) Wireless Telegraph Company in this country; 
and in Germany as the Gesellschaft fur drahtlose Telegraphie (Sys¬ 
tem Telefunken). There are at present about 600 sets of the Tele- 
funken wireless apparatus in operation in various parts of the world, 
including land stations, shipboard, lighthouses and portable military 
installations. 

The main difference between the various high-class commercial wire¬ 
less telegraph systems to-day (1909) may be said to consist quite 
largely in details of circuit arrangement and in the quality of ap¬ 
paratus employed by the various companies. A number of improve¬ 
ments have been added to the Telef unken system since it was de¬ 
scribed in the preceding pages, and as these improvements correspond 
more or less with the recent general advance in the art of spark wire¬ 
less telegraphy a somewhat full description thereof will now be given. 
A description of the most recent addition to this company’s wireless 
methods, the singing spark system, will also follow. 

The Telefunken Transmitting Circuits. —It is well understood that 
the type of apparatus and arrangement of the various wireless systems 
are still undergoing more or less change as practical experience dic¬ 
tates. Fig. 1, however, may be considered as fairly representing the¬ 
oretically the present transmitting circuits and apparatus of the Tele¬ 
funken Company as installed in many shore stations and on ship¬ 
board, including a number of ships of the United States Navy. 

In many of these installations the oscillations are primarily excited 
by an alternating current generator g, driven by an electric motor M 
(motor-generator). The motor receives its current from the power 
wires e e, frequently connected with the ship dynamo machine. 


TELEFUNKEN CIRCUITS. 


103 


In the particular installation shown the thick lines indicate the cir¬ 
cuits of generator g and of motor M as arranged for the Crocker- 
Wheeler type of motor-generator. When the motor starter ms is 
operated, current from the mains e e flows through the motor m, the 
speed of which is regulated by the field resistance regulator fr. Sim¬ 
ilarly, the voltage of the generator g is regulated by its field rheostat 
fr'. v is a voltmeter, used to indicate the voltage in the primary 
circuit of a resonance transformer t. This transformer is shown as it 
appears in practice in the section on Transformers, Chapter XIV. k 
is a Morse telegraph key in the primary circuit of the transformer. 



Fig. i.—Telefunken Wireless Transmitting Circuits. 

This key opens the circuit without excessive sparking with a current 
of 25 amperes and 110 volts, c represents a battery of Leyden jars in 
the primary oscillation circuit, s is the spark gap. This oscillation 
circuit is connected by more or less close coupling as desired to the 
aerial a. In some systems a variable induction coil or oscillation trans¬ 
former is used in place of l for very loose or indirect coupling. The 
Telefunken company employ for this purpose two independent coils 
of heavy bare copper wire with widely separated spirals and with one 
of the coils movable outside of the other for varying the coupling. 
The inductance of the closed oscillation circuit s l c is supplied by 
turns of the coil t', adjustable by clips g g. Inductance is also sup¬ 
plied to the aerial circuit by the coil t', the amount of which may be 
varied by the clips t V . A portion of this coil is common to both the 
aerial and the closed oscillation circuits. In some cases a special 
lengthening out inductance coil is used in the aerial. A hot wire 
ammeter h may be inserted between the vertical wire and earth (or a 
counterpoise). 

In arranging for given installations the usual practice is to pre- 

















































104 


WIRELESS TELEGRAPHY. 


determine as nearly as feasible the wave length to be employed, and 
to design and adjust the aerial and transmitting apparatus accord¬ 
ingly. For instance, the United States Navy has adopted 425 meters 
(1,394 feet) as a standard wave length. This is about equal to a fre¬ 
quency of 700,000 cycles per second. (See Table of Wave Lengths, 
at end of Part I.) To adjust the aerial and the transmitter oscilla¬ 
tion circuits to the desired wave length the wave meter is utilized. 
(See page 313.) For this purpose oscillations are set up separately in 
the respective circuits and the adjustments are then made as required, 
by varying the position of the clips g g (Fig. 1) on the spiral in¬ 
ductance t' for the primary oscillation circuit, and the clips t V for 
the aerial circuit. The two circuits are then “coupled,” as indicated 
in the figure, when further adjustments will be necessary owing to 
variations in the inductance due to mutual reactance of the turns. 
Resonance will be indicated between the circuits at maximum reading 
of the hot wire ammeter h. To vary the degree of coupling between 
the circuits the clips t V may be moved uniformly up or down along 
the turns of the spiral without varying the distance between the clips. 
The fewer the turns of the spiral enclosed by t V that are enclosed 
by g g, the looser is the coupling. In the figure the coupling is com¬ 
paratively tight. 

In some installations of this system the spark gap is placed in the 
position occupied by condenser c in Fig. 1, and condensers are placed 
on each side of the spark gap next the inductance. To avoid injury 
to the coils of the generator g or motor m by high potential discharges 
their coils are shunted by two carbon rod resistance cr having a 
ground connection between them, rc indicates the wires leading to 
the receiving circuits. To prevent accidental connection between the 
transmitting and receiving circuits the device shown at switch s' 
is provided. In the vertical position of the arm of the switch the 
wires x x are joined by a metal blade and the primary circuit of trans¬ 
former t is closed at that point. When the switch arm is moved to the 
horizontal position the blade leaves wires x x, thereby opening the 
primary circuit. In the horizontal position of the arm its outer end 
makes contact with a terminal of the receiving circuit rc, a removable 
plug and wire attached to the switch connecting the receiving system 
with the aerial a above the small anchor or air gap a. This air gap has 
but little if any effect in damping outgoing high potential oscillations, 
but it effectually diverts incoming high potential oscillations to the 
receiving circuit. 


TRANSMITTER APPARATUS. 


105 


Multiple spark gaps have been quite thoroughly tested by this com¬ 
pany, but experience has indicated that in general the more satisfac¬ 
tory results are obtainable with the single spark gap. With the mul¬ 
tiple spark gap it was, for instance, found that the discharge was not 
always simultaneous in the different gaps; this affecting the efficiency 
of signaling. The difficulty of adjustment of the spark was also in¬ 
creased. The spark discharger now largely employed in the Tele¬ 
funk en and other systems consists of two brass rods, sometimes tipped 
with about one inch of zinc. The rods are about .4 inch in diameter. 
Zinc tips are employed mainly because of the non-arcing property of 
the metal, due to the high resistance of zinc vapor. The spark gap is 
usually enclosed in a case the door of which is closed to deaden the 
sound. The inductance, capacity and spark gap of the transmitter 
oscillation system are frequently grouped for compactness on ship¬ 
board as shown in Fig. 2 (in shop phrase, the “tub” arrange¬ 
ment). The spark discharger is contained in the case c'; a 
battery of 7 small Leyden jars in multiple is enclosed in a 
hard rubber case c. A large spiral copper wire inductance, about 
25 inches in diameter, is placed, as shown around the cylinder c. 
The amount of inductance in use is 
varied by changing the position of 
the clips t V on the spiral, wedges 
or pins w being arranged at in¬ 
tervals around the spiral for this 
purpose. To facilitate this adjust¬ 
ment further the clip V is con¬ 
nected by a flexible wire with a mov¬ 
able ring m' which in turn is con¬ 
nected to the aerial wire, and clip t 
is similarly connected with a mov¬ 
able ring m attached to a spark rod, 
by which arrangement the clips can 
be conveniently placed at any point 
on the coil, h is a rod by which the 
length of spark gap is adjustable; 

V is connected with the spark rod; 

Z is a means of short circuiting cer- 
tain of the spark gaps, when mul¬ 
tiple gaps are employed, plugs n are connected with one side of the 
Leyden jars. A pair of conductors x carry current to a fan motor in the 
lower part of the tub to drive off hot vapors and ionized air at the spark 









106 


WIRELESS TELEGRAPHY. 


gap. This apparatus has a wave range of from 393 feet to 3,280 
feet. (120 meters and 1,000 meters, respectively. 1 meter equals 
3.28 feet.) 

Telefunken Condensers. — Specially constructed Leyden jars are 
used for capacity in the transmitter oscillation circuit in this system. 
The standard jar for outfits up to 5 kilowatts is 14.5 inches high and 
4.6 inches in diameter. The capacity of these jars is .002 microfarad. 
For a 1.5 kilowatt 60-cycle installation 3 jars are used in parallel; 
for a 1.5 kilowatt 120-cycle installation, 3 jars in parallel in series of 
2 are employed. For a 2.5 kilowatt 60-cycle outfit, 7 jars in multiple 
are used. For a 5 kilowatt transformer at 60 cycles a capacity equal 
to 3 or 4 small jars is utilized; for instance, 3 such jars in multiple in 
series of 3. For installations exceeding 5 kilowatts the standard jar 
is 4 feet 8 inches high and 4.25 inches in diameter, with a capacity of 
10,000 centimeters or .011 microfarad. The arrangement of these 
jars is variable, depending on requirements. A common way is to 
use 9 such jars, 3 in multiple in series of 3, giving a resulting capacity 
equal to one of the jars, that is .011 microfarad. In the Nauen high 
power station, described further on in this section, a battery of 360 
large jars is arranged with 120 jars in multiple, in series of 3. As 
each jar has a capacity of .011 microfarad, the resulting total capacity 
in the oscillation circuit is .044 microfarad. 

The object of arranging condensers in series (or cascade) in high 
potential circuits is to divide the pressure between two or more con¬ 
densers; thus if the potential at the terminals of the secondary of the 
transformer is 30,000 volts each condenser in a series of two would be 
subject to a pressure of 15,000 volts, or if in series of three to a 
pressure of 10,000 volts. The rating of condensers and inductance 
coils is frequently given in centimeters in accordance with the system 
of absolute electromagnetic units. To reduce the capacity in centi¬ 
meters to microfarads divide centimeters by 90,000. To reduce induc¬ 
tance in centimeters to microhenrys divide centimeters by 1,000. 

Owing to the fragile nature of tin foil and the consequent defects 
due to injury by abrasion, this material is being supplanted by a double 
coating of silver and copper inside and outside of the jars. These 
coatings are placed on the glass in several different ways. For in¬ 
stance, the silver is deposited on the glass by a chemical process and 
burned in at a temperature of about 1,000° F. A coating of copper 
is then electroplated on the silver. In other cases, mats of copper and 


RECEIVING CIRCUITS. 


107 

silver are first laid on the glass mechanically, after which a heavy 
coating of copper is put on by the electroplating process. These 
methods afford a strong, durable and air-tight coating. The capacity 
of the jars is not materially affected by the substitution of copper for 
tin foil. 

Telefunken Receiving Circuits. — The Telefunken receiving ap¬ 
paratus for loose and close coupling respectively are outlined in Figs. 
3, 4. In Fig. 3, a is the antenna, s' is a throw over switch, v is a 
tuning coil, termed the variometer, for effecting a variation of the 
induction for tuning. In one form employed in this system this 
device consists of two coils of equal turns of wire, one coil being fixed, 
the other mounted on a pivot. The coils are connected in series, but 
by means of the pivoted arrangement of the movable coil the in¬ 



ductive effect of the one coil may be made to coincide with, or to 
oppose, that of the other to a desired degree, thereby varying the in¬ 
ductance of the circuit. (See Variometers, Chapter XIV.) c is a 
variable condenser, p and t are the primary and secondary of a 
hinged tuning or oscillation transformer t, described subsequently, c 
is a variable condenser in the receiver oscillation circuit, d is a de¬ 
tector of the electrolytic or other suitable type, shunted by a variable 
condenser c and condensers c '; the latter may be switched in or out of 
circuit as desired by switches 5. clc are small choke coils commonly 
used to divert oscillation currents from the circuit of telephone r. 
p' i s a potentiometer controlling battery b. One cell of this battery is 
outside the control of the potentiometer; the others are variable as 
indicated. With the exception of the hinged tuning coil t, the ap¬ 
paratus in Fig. 4 is similar to that of Fig. 3. Many efficient varia¬ 
tions of the variometer coupling arrangements are of course available; 
for instance, that shown in Fig 4 a in which l V are respectively the 




































108 


WIRELESS TELEGRAPHY. 


pivoted and fixed coils of a variometer, c is a variable condenser, d a 
detector. 

In the hinged transformer for loose coupling shown at t in Fig. 3 
and at n w in Fig. 7, the desired variation of the coupling is obtained 
by moving the coil p to or from the fixed coil t. The number of 
turns of wire in service in the primary of this transformer is also 
variable by means of plugs and cords. (See Fig. 7.) Another re¬ 
ceiving oscillation transformer employed by this company consists of 
a fixed secondary coil, Fig. 5, mounted on a core c, 4 inches in diame¬ 
ter. A primary coil p is movable on two vertical guides w w, to and 
from the fixed coil. In one position the movable coil may entirely 



Fig. 4 a . 


Fig. 5.—Receiver Oscillation Transformer. 



surround the fixed coil or it may be removed any distance up to 6 
inches below it. Each coil is adjustable as to the number of turns of 
wire in use by means of plugs n n, inserted in a desired contact. 
These tuning coils are provided in different sizes according to the 
wave length employed at a given station. By means of these devices 
the inductive relation of the primary to the secondary coil may be 
graduated by very minute stages until all waves but those to which 
the receiver is attuned are eliminated, thereby reducing interference 
to a minimum. To lessen the damping of oscillations in the receiver 
circuit a stranded wire of very low resistance wire is used in the 
secondary. 















FILINGS COHERER CIRCUITS. 


109 


In Fig. 5 s is a switch, by turning the handle h of which the cir- 
-cuits may be quickly changed from loose to tight coupling, for in¬ 
stance, from the arrangement of circuits shown in Fig. 3, to that 
shown in Fig. 4. In practice it is often found that under certain 
conditions better signals are received with the direct than with the 
inductive connections, and contrariwise, depending on the nature of 
the transmitted signals. This remark also holds good in many in¬ 
stances in transmitting signals. For actual practice, especially on 
shipboard, the open circuit transmitter is largely employed with satis¬ 
factory results, especially in fair weather. 

The Telefunken Receiving Circuits with Filings Coherer and Ink- 
Writer. —These circuits are outlined in Fig. 6. a is a flexible wire 
leading to the antenna and which wire by means of a plug n is in¬ 
serted in the arm of switch s'. In a horizontal position this switch 
connects the aerial wire as shown with the receiving apparatus, 
-etc., and as explained in connection with Fig. 1. p is the 



Fig. 6.—Filings Coherer Receiving Circuits. 


primary of a hinged oscillation transformer t in the antenna 
circuit, s is the secondary thereof, c' is a variable air con¬ 
denser in the aerial for tuning, or shortening of the wave length of 
the aerial when necessary, c is a condenser parallel with the coherer 
and of so large a capacity compared therewith that the effect of an^ 
variations in the coherer capacity may be neglected, thereby main- 











































110 


WIRELESS TELEGRAPHY. 


taming a practically uniform inductance and capacity in the receiv¬ 
ing oscillation circuit, c is a small mica condenser that provides an 
oscillation circuit around the relay r, hut does not prevent the opera¬ 
tion thereof by the coherer, r is a polarized relay in series with a 
granular coherer in an exhausted tube k. (See page 90.) r' is a 
resistance of 6,000 ohms in the relav circuit to reduce the current 
strength therein, thereby also reducing the spark energy at contacts 
v of the tapper m. The armature lever of relay r operates the tapper 
M and the Morse register, or ink writer, m', at contact m, practically 
as described fully herein in connection with other systems (page 54). 
The sensitiveness of the relay may be tested by introducing into its 
circuit the resistances r r' of 50,000 ohms each, switches d d', being 
operated for the purpose, at which time the coherer is cut out by 
switch d'. The relay is then adjusted to best working conditions. 
This relay will operate with 1.4 volt through a resistance of 100,000 
ohms. The breaking of the coherer and relay circuit at contact v 
of the tapper is found to facilitate signaling. (See page 127, Branly 
coherer connections.) Polarization cells g are placed across the ter¬ 
minals of magnets m and m' to minimize sparking at contacts m due 
to the discharge from their coils. These cells consist of small sealed 
phials containing a solution of sulphuric acid into which dip two 
platinum wire electrodes. The receiving aerial circuit is tuned to 
a desired wave length by suitable adjustment of the hinged inductance 
coil t and capacity c', and the secondary oscillation circuit is tuned 
to corresponding wave lengths. a r are small switches for opening 
local circuits when not in use. 

The tilings coherer has been largely supplanted as a receiver of sig¬ 
nals by various auto detectors and the telephone receiver, but is still 
employed when a record or call bell, or alarm, are desired. 

Telefunken Wireless Apparatus.— The Telefunken transmitting key 
K and the receiving instruments as arranged in practice for shipboard 
and other station use, are shown in the reproduced photograph Fig. 7. 
A combined coherer ink recording device and electrolytic or thermo¬ 
electric detectors with telephone receiver are here illustrated. In this 
combined arrangement the primaries p p of Figs. 3, 4 are placed in 
series. Otherwise the circuit connections are virtually as shown in 
those figures, a is the lead to the aerial wire, l is a variable con¬ 
denser in parallel with the auto detector and the secondary of receiv¬ 
ing transformer n'. n is the hinged primary thereof, in the aerial. 


PHOTO-ELECTRIC RECORDER. 


Ill 


s is a variable condenser in series with the aerial and the tuning coil l. 
I is common to both receiving circuits, o is a condenser in series with 
coil l. w' is the secondary thereof. There is a small condenser in 
the base of w' in parallel with coherer and w'. u is the coherer relay. 
p is the aerial switch, r is an inking recorder; j is a back stop for its 
armature, k is the Morse transmitting key. m is the coherer, a is a 



Fig. 7.—Telefunken Wireless Apparatus. 

switch arm on telephone receiver, x indicates the location of the auto 
coherer, t is a head telephone. In general the auto detector ap¬ 
paratus is on the left side of table; that of the coherer on the right 
side. 

Telefunken Photo-Electric [Recorder. — Quite recently the Tele¬ 
funken Company has placed on the market a detector capable of oper¬ 
ating a very sensitive relay which in turn starts a clockwork train 
and other apparatus that produces a photographic record of the sig¬ 
nals. Briefly, this is done by causing the relay to operate a shutter 
of a camera that throws light on or shuts light from a moving sensi¬ 
tized ribbon film. The ribbon passes through the proper solutions 
after it emerges from the camera, and in a few seconds the received 
message, in dots and dashes, is developed. It may be noted that Dr. 
Siebt has also devised a photographic recorder of wireless signals in 
which the electric waves are caused to deflect a fine wire, the move¬ 
ments of which throw shadows that are reproduced as dots or dashes on 
a sensitized paper ribbon. 












112 


WIRELESS TELEGRAPHY. 


THE NAUEN HIGH POWER STATION. 

This station of the Telefunken Wireless Company was established 
chiefly for experimental purposes. Nauen is 25 miles from Berlin, 
northwest. Wireless telegraph signals have been received from this 
station on board the S. S. Bremen at a distance of 1,488 miles, much 
of which distance was overland. Signals have also been heard from 
Nauen in St. Petersburg, distant 837 miles overland, and at Rigi, 
Scheidegg, Switzerland, 496 miles, mainly over mountains. 

At the Nauen station marshy ground is found 6 feet below the 
surface, this affording an excellent earth. The antenna of this sta¬ 
tion is supported by an iron latticework tower t; Fig. 8. The tower 
is triangular in form, each side of the triangle being 13 feet long. 
Each of the 3 vertical side girders, formed in sections 28 feet in length, 
are bolted end to end and are connected with one another by diagonal 
cross stays. Within 19 feet of the ground the girders join in a cast 
steel ball b, which rests on a socket c. The weight of the tower is 
carried through a layer of insulation to a solid concrete foundation. 



Fig. 8.—Nauen Station Antenna Umbrella Type. 


The tower is kept in a vertical position by three guys attached to the 
tower 246 feet from the earth, not shown in figure. The guys are 
anchored by means of heavy masonry at a distance of 656 feet from 
the base of tower. The guvs are insulated from the tower and from 
the anchorage. On account of the high potential employed at this sta¬ 
tion, which sometimes produces a spark 39 inches in length, the upper 
ends of the guys are insulated in oil. The antenna a is of the um¬ 
brella type. The umbrella portion of the aerial is arranged in 6 folds 
or segments, as indicated, spreading out from the top of the tower. 
Each segment of the antenna is held out from the tower by means of 
hempen ropes r attached to iron posts n in the ground. Porcelain 






FREQUENCY METER. 


113 

knobs i insulate the rope from the earth and antenna. Each segment 
may be raised or lowered by pulleys p. The upper part u of the an¬ 
tennae is composed of 6 Xo. 9 B and S phosphor-bronze cables. Lower 
down, this cable branches into 3 smaller cables as indicated at in. 
The vertical wires proper consist of 6 cables connected to the um¬ 
brella antenna, at the top of the tower, and which are brought down 
to the foot of the tower, where they are united and thence are led into 
the operating room h. The vertical wires are not insulated from the 
tower, hence the tower itself is part of the oscillation circuit. The 
total surface covered by the antenna is about 642,000 square feet. The 
earth or ground is formed of 108 wires spreading out radially from 
the base of the tower, covering an area of over 1,300,000 square feet. 

The source of power for this station is a 25 kilowatt generator, 
driven by an oil engine, and giving 60 cycles at 750 revolutions per 
minute. Four induction coils, or transformers, are employed for the 
exciting current, the primary coils of which are connected in series. 
Alternating current is supplied to these coils by the generator through 
4 large choke coils. The 4 secondary coils of the transformers are 
connected in multiple with one another and in series with 2 high ten¬ 
sion choke coils and the battery of Leyden jars and the spark gap. 
The operator in signaling manipulates a Morse key, which in turn 
operates a solenoid switch. This switch cuts off current from the 
Leyden jar circuit by simultaneously short-circuiting the primary 
coils of the transformers and the winding of the generator through 
the said choke coils, which action is equivalent in effect to opening 
the primary circuit by the Morse key. The receiving apparatus of this 
station is practically similar to that already described. 

Frequency Meter.— To aid in obtaining tuning a low frequency 
meter is employed in the generator circuit of this and certain other 
svstems. This meter, briefly described, in one form, consists of an 
electromagnet placed in the generator or other circuit. In proximity 
to the electromagnet a large number of small iron or steel rods, or 
reeds, are arranged side by side vertically and fixed at their lower 
ends. Each reed is attuned to a certain note, or rate of vibration. 
It is known that reeds (or armatures) so arranged will vibrate only 
to the pulsations of magnetism to which they are attuned. The upper- 
ends of the reeds are seen through a glass window in the top of the 
case in which the instrument is enclosed, and opposite each reed is 
marked on a scale the number of cycles to which it responds. Since 


114 


WIRELESS TELEGRAPHY. 


the electromagnet controlling these armatures is in the alternating 
current circuit, obviously magnetic alternations corresponding to the 
current alternations will occur in the magnet, and that reed which is 
attuned to the existing frequency of the circuit will vibrate, thereby 
visually indicating that frequency. 


TELEFUNKEN WIRELESS TELEGRAPH FROM MOVING RAILWAY TRAINS. 

In this country De Forest and others have made experiments with 
wireless telegraphy as a means of communicating with railway trains 
in motion. In Germany also, as mentioned in Chapter XV, consid¬ 
erable work has been done in this direction, the object being to in¬ 
crease the safety of railway traffic. In the Telefunken experiments 
the aerial wire a for the fixed station is suspended between two railway 
telegraph poles p p, Fig. 9, and about 12 inches below the telegraph 
wires, by means of a hempen rope c, and porcelain insulators b. A 
leading in wire d connects the aerial wire with the instruments in an 
adjacent cabin c. The length of the aerial wire is 200 feet. The 
outgoing signals from c follow the telegraph wires to the moving 
train and vice versa. The transmitting circuit is outlined in Fig. 10. 
b is a 16 volt storage battery. . The current output with a spark gap s' 



Figs. 9, 10.—Telefunken Railway Wireless Circuits. 


of .114 inch is 2 amperes, v is a voltmeter across the battery, k 
is the Morse key. 1 is the induction coil; i is its interrupter, shunted 
with the usual condenser c' to prevent sparking, c is a capacity con¬ 
sisting of 8 Leyden jars, l is a variable inductance for tuning. The 
natural wave length of the aerial circuit, including the coupling coil 
l, is 1,148 feet, to which wave length the closed oscillation circuit is 
also adjustable. 

The aerial wire on the train is arranged on the roof of a car in the 
shape of a rectangle, being upheld by porcelain insulators on the top 
of vertical rods about one foot long on the corners of the roof of the 
car. The receiving circuits, loosely coupled, are practically as shown 
in Fig. 6. 




















SINGING SPARK. 


115 


In these experiments no appreciable difference in the signals was 
noted when the aerial wire was brought nearer the roof of the coach, 
but a perceptible difference was noted when the length of the aerial 
wire was varied. The maximum distance at which signals could be re¬ 
ceived during these experiments was 7.5 miles. Bridges between the 
transmitter and receiver did not appear to affect the signals. When 
there are many tracks, as in railway stations, it was not feasible to 
use the telegraph wires for the transmission of the waves, but in such 
cases a wire laid close to the rails and parallel therewith will carry 
signals for a distance of 1.8 miles. 


TELEFUNKEN SINGING SPARK SYSTEM. 

The Telefunken Wireless Telegraph Company, through Count Arco, 
has recently announced the introduction by that company of a new 
method of wireless telegraph transmission. (See “Electrotechnische 
Zeitschrift” Nos. 23, 24, 1909.) This new method consists essen¬ 
tially of a multiple spark gap consisting of a number of flat discs 
separated by a thin ring of mica. These gaps receive current from 
an induction coil of about 250 cycles and about 2,000 to 3,000 volts 
or more as required. The gaps are shunted by a small capacity and 
inductance. More or less of the gaps may be cut out and the space 
between them may be varied, or resistance may be introduced in series 
with them, to regulate the intensity. To obtain high heat conducting 
qualities the metal employed for the discs is copper or silver. Full 
details of this system are at present lacking. In experiments by Flem¬ 
ing 11 gaps were used consisting of copper plate about 5 inches in 
diameter separated by mica rings .01 inch thick. 

The term applied to this Telefunken oscillation generator is 
“quenched” spark. It is also termed the “sounding” or “singing” 
spark generator, as it gives out a clear musical tone, which may be 
varied at will. Precedence in the employment of this adaptation of 
Wein’s discovery in 1906, that very powerful discharges with ad¬ 
vantageous properties for wireless telegraphy could be obtained with 
very short spark gaps, is claimed by representatives of the Yon Lepel 
Wireless Telegraph system, subsequently described. (See Telefunken 
German Patent No. G 27483, 1909, and Yon Lepel German Patent 
No. 24757, 1909.) 



116 


WIRELESS TELEGRAPHY. 


The transmitting and receiving circuits of the singing spark system 
are outlined in Figs. 11, 12. In Fig. 11 t is the induction coil, s 
represents the spark gaps, d the discs, m the mica rings, c is a paper 
condenser, l is a variometer or variable inductance, coupling the pri¬ 
mary oscillation circuit to the aerial. V is an additional coil in the 
aerial for varying the wave length, h is a hot wire ammeter. The 
variometer is of peculiar construction, consisting of a fixed and a 
movable plate, on which are placed four coils which may be arranged 
in series or in multiple. In certain positions of the plates the four 



Figs, ii, 12, i 2a. —Singing Spark Transmitting and Receiving Circuits. 


fields are added and the inductance is a maximum; in an opposite 
position the inductance is a minimum. By means of this arrange¬ 
ment and keeping capacity c constant the wave length may be varied 
from 500 to 2,000 meters. A small inductance l in the primary oscil¬ 
lation circuit is employed to maintain loose coupling with short wave 
lengths, k is a telegraph key in the alternating current generator 
circuit. 

Two arrangements of receiving circuits are shown in Fig. 12 
and Fig. 12 a; the first for a short wave length, the second for a lone; 
wave length. In the reception of signals transmitted by the singing 
spark method any of the well-known receivers may be utilized." A 
special receiver d has, however, been designed, of the thermo-electric 
or contact type, to receive over a wide range of wave lengths (from 200 
to 3,000 meters) with a very small loss from damping in the tuning 
arrangement. According to Count Arco this detector is about 20 per 
cent, more sensitive than the electrolytic type and is very constant. 
In connection with this system also, a calling apparatus consisting of 
a selective bell that rings when a station calls for 10 seconds, but does 
not respond to atmospheric disturbances or to the re°rilar Morse sm- 





















SINGING SPARK APPARATUS. 


117 


nals is employed. A resonance relay that intensifies the weakest sig¬ 
nals while still keeping them as clear musical notes is also one of the 
features of this new system. 

The transmitting apparatus of a 2-kilowatt outfit as it appears in 
practice is shown in Fig. 13. The space occupied by this apparatus 
is 28 inches lengthwise by 15 inches in height and 15 inches in width. 
The sparking discs are indicated by s; the paper condensers are con¬ 
tained in box c (owing to the low voltage used paper condensers may 
be utilized), v is the sender variometer, l are inductance coils. 

The receiving apparatus is shown in Fig. 14. l is a hinged tuning 
coil, w w' are the short and long wave switches, s is the usual cut¬ 
out switch, c is the handle by which the plates of a variable con¬ 
denser are adjustable, d is the detector. 



.Figs. 13, 14.— Telefunken Singing Spark Iransmitting and Receiving 

Apparatus. 


Amongst the advantages claimed for the singing spark by Count 
Arco are the following. Smaller aerials. With arc lamp installations 
practical experience shows that the height of mast for given dis¬ 
tances must be, say, 300 to 330 feet; with the new method one-half 
that height will suffice. The reason for this is that nominal energy 
from the arc lamp oscillator can only be generated when the wave 
length is very great, necessitating high aerials; while the singing 
spark works efficiently with long or short waves. Again, the singing 
spark allows a high efficiency to be obtained, and, depending on the 








118 


WIRELESS TELEGRAPHY. 


size and suitability of apparatus, from 50 to 75 per cent, of the ma¬ 
chine output can be delivered at the aerial, as compared with 20 per 
cent, by the ordinary spark system and 10 per cent, by the arc lamp 
arrangement. Further, the wave emitted by the singing spark shows 
a very small damping decrement, between .08 and .025, this permit¬ 
ting sharp tuning. Also the oscillations therefrom remain absolutely 
constant and are independent of the arrangement and mechanical 
properties of the spark gap, and very much greater freedom from 
disturbance (2 to 5 per cent.) can be obtained with the singing spark 
than with the arc lamp. In the latter the theoretic freedom from 
local disturbances is ^2 to 1 per cent., but because the frequency does 
not depend on the electric constants alone, but also on the arrange¬ 
ment, length and other properties of the arc, the actual freedom from 
disturbance is 5 to 6 per cent, and even that is not always obtained. 
The singing spark also allows a large range of oscillations to be ob¬ 
tained, whereas with the arc oscillator only certain fixed waves can 
be sent out. The singing spark also possesses the advantage that the 
regulation of the intensity or amplitude of the oscillations produced 
thereby may be regulated very readily between wide limits. For in¬ 



stance, a station having a range of several thousand kilometers may 
have its intensity reduced so that signals will not be heard beyond 100 
kilometers. Inasmuch as the singing sparks give a musical tone, the 
reception of signals through atmospheric disturbances is facilitated. 
This also allows of multiple reception of signals on one antenna as 
signals with, say, a frequency of 500 per second from one station may 
readily be distinguished from those of a frequency of, say, 1,000 per 
second from another station. Obviously also, as noted elsewhere, no 
ticker or interrupter is necessary with the singing spark. Count Arco 
also points out that the quenched spark transmits but one wave and is 


























































VON LEPEL SYSTEM. 


119 


thus different from the spark sender that transmits two coupled 
w r aves; hence multiple telegraph transmission is simplified. This effect 
is illustrated in the accompanying diagrams in which p s' Fig. 15 
represents the oscillations in the primary and secondary oscillation 
circuits of the ordinary spark gap, and p s Fig. 16 the oscillations in 
the primary and secondary oscillation circuits of the quenched spark, 
in inductively coupled circuits. (See Section on Transformers, Chap¬ 
ter XIV; also Von Lepel Generator herein.) Again, a disadvantage 
of the arc lamp method is that with high energy transmission ex¬ 
cessive damping on long wave lengths and irregularities of many 
kinds occur, since at high voltages and with strong currents the arc 
lamp is unsteady, and the great development of heat gives rise to rapid 
burning away of the electrodes. These inconstant conditions also 
affect the frequency, for which reason the arc method has not been 
used in high power stations thus far. 

With apparatus of the singing spark type it is expected that an 
8-kilowatt outfit with masts 200 feet high will have a range of about 
1,675 miles over level land or sea. It is also expected that it will be 
feasible to receive two or more different messages in one detector by 
utilizing the tone feature of this system. 


THE VON LEPEL WIRELESS TELEGRAPH SYSTEM. 

The most important feature of this new wireless system consists of 
the Von Lepel oscillation generator. This ingenious device is based on 
the discovery by Wein in 1906 that very powerful discharges with 
advantageous properties for wdreless telegraphy could be obtained from 
very short spark gaps. One arrangement designed by Von Lepel to 
avail of this discovery is shown in the section on sustained oscilla¬ 
tions, Part 2, page 11. As stated therein this device consists of a 
metal box having a partition of 2 copper plates separated by a very 
thin sheet of paper having a small aperture in its centre. In opera¬ 
tion the paper (one or two sheets may be used) gradually burns away, 
but it lasts for two or three hours without renewal. Another form of 
the Von Lepel generator consists of two metal plates or electrodes 
about 3 inches in diameter and separated by thin sheets of paper. 
The gaseous space between the plates in operation is about .002 inch, 
but this space may be varied within comparatively large limits without 



120 


WIRELESS TELEGRAPHY. 


■appreciably changing the frequency of the current. The upper plate 
•consists of brass or other alloy when direct current is employed. This 
plate is cooled by contact with a water tank, while the lower plate 
forms the cover of a cup in which water is circulated. All of which 
•conditions combine to constitute thh device a very efficient spark ex¬ 
tinguisher and arc preventer. No load tests of this generator show 
the large decrement of oscillations in the primary circuit of .6, ob¬ 
tained solely by a proper proportioning of the inductance and capacity. 
(Decrement of oscillations in brief is found from the ratio of the 
amplitudes of two successive half waves, sometimes termed the 
attenuation ratio, which is written as the logarithmic decrement 


s = 



where w represents the energy losses due to heat 


.and radiation, c is capacity and l is inductance of the circuit.) 

Many points of advantage are claimed for this (or possibly a some¬ 
what similar) type of oscillation generator over the arc lamp oscilla¬ 
tion generator, or the ordinary spark gap method, some of which are 
noted in the preceding pages. (See Telefunken Singing Spark sys¬ 
tem.) An important point is that owing to the rapid damping or 
quenching of the spark between the electrodes, the primary oscilla¬ 
tion circuit ceases to give out energ} 1, after the first blow, so to speak, 
while the secondary, or aerial, oscillation circuit continues to oscil¬ 
late; virtually as one might pluck or strike a tuning fork at inter¬ 
vals and quickly withdraw the fingers or rod. A practical advantage 
of this is that in coupled circuits it has been found that but one set 
of oscillations is radiated. (See Figs. 15, 16.) 

An entirely satisfactory explanation of the phenomena of this oscil¬ 
lation generator is not yet forthcoming. It has been suggested that it 
partakes of the nature of the Poulsen arc, the slow burning of the 
paper providing an atmosphere of hydrogen, but Yon Lepel has shown 
that sparks occur without the intervention of the paper, or other in¬ 
sulating medium. The introduction of the insulating medium is 
found to prevent a tendency of the discharge to move to the edge of 
the plates where it would form an arc. Mica has been used by Yon 
Lepel for this purpose, but he finds that on being fused by the dis¬ 
charge it becomes conducting. On the other hand, the burning away 
of the paper constantly presents new and cool spots on the plates for 
the discharge. 

The transmitting and receiving circuits and apparatus of the Yon 
Lepel wireless telegraph system are outlined in Figs. 17, 18. In Fig. 


VON LEPEL CIRCUITS. 


121 


17 b V represent the Yon Lepel generator, a is the aerial. I is the 
aerial tuning coil, l and 1/ are coupled spiral inductances, c is a 
capacity in the oscillation circuit, k is a telegraph key. g is a direct 
current generator developing 400 volts and about 2 amperes. An 
alternating current may be employed. The capacity c and inductance 
i/ are very small. 

In Fig. 18 a is the aerial, c c' are variable condensers. V V are 
oscillation transformers in the circuits x y z. Circuits x y are tuned; 
the detector circuit z is not tuned, but will respond to any frequency. 
d is a sensitive thermo-electric detector. 



Figs. 17, 18. —Von Lepel Transmitting and Receiving Circuits. 


In recent experiments A 7 on Lepel has found it possible to produce a 
quickly variable, low rate of oscillations by this generator, bringing 
them within the range of audibility, and thereby avoiding the necessity 
of a ticker or interrupter for wireless telegraphy. With 800 watts in 
the supply circuit, 250 to 300 watts are developed in the oscillation 
generator circuit, this indicating an efficiency of about o5 per cent, as 
compared with 10 per cent, in the arc lamp oscillator. This system 
has been for some time in use by the German Army. Two experi¬ 
mental stations have been operated in Great Britain where signals 
have been transmitted to a distance of 100 miles overland. In Ger¬ 
many signals have been transmitted over 300 miles by this system. 
Owing to the high efficiency of this generator Yon Lepel finds that 
much smaller aerials than heretofore necessary can be employed. 

These methods of developing electric oscillations in wireless teleg¬ 
raphy are, it may be said, still in their incipiency, and it remains to 
be seen whether in general practice they will beai out the promises 
and hopes of the inventors. 






















122 


WIRELESS TELEGRAPHY. 


PORTABLE WIRELESS TELEGRAPH OUTFITS. 

Portable wireless outfits are usually designed for military purposes, 
and consequently special attention must be given to the features of 
lightness, handiness of apparatus, reliability, durability, simplicit}^ of 
parts, efficiency with comparatively small outlay, and general useful¬ 
ness on the field. 

The Telefunken Portable Station. — To comply with the foregoing 
requirements a Telefunken portable station is divided into four parts. 
The aerial wire net, the source of energy, the transmitting and the 
receiving apparatus. The mast for the support of the aerial wire net 
consists of 7 magnalium rods (an alloy of aluminum and mag¬ 
nesium), each rod 8 feet 3 inches long, giving a height of 



Fig. 19.—Portable Transmitting and Receiving Circuits. 


about 50 feet in all. An umbrella antenna consisting of 6 bronze 
wires, each 82 feet long, is used. A counterpoise consisting 
of 6 wires, each 131 feet long and suspended 3.28 feet above 
the ground, is employed; the wires extending radially from a metallic 
ring around the mast, from which the counterpoise is insulated. The 
weight of the mast is 66 pounds. The antenna is held in position by 
suitable guy wires. The counterpoise is employed because of the diffi¬ 
culty in obtaining good earths in many places, also to minimize 
atmospheric disturbances. Power is supplied by a small self-exciting 
generator, giving 150 watts at a speed of 1,300 revolutions per min¬ 
ute. The generator is driven by 2 men by means of a tandem bicycle 
treadle and gearing. Leyden jars immersed in oil to obtain maximum 
efficiency are employed in the transmitter oscillation circuit. 






































PORTABLE OUTFITS. 


123 


The transmitting and receiving circuits of this portable outfit are 
outlined in Fig. 19. They are theoretically similar to the transmit¬ 
ting and receiving circuits of this company already described. In 
the figure g is the generator, co' is a cut-out switch, hf is a pro¬ 
tective device against high frequency discharges; it is connected to the 
frame g of the generator, r is a pilot lamp showing that power is on 
or off. k is the Morse telegraph key. t is the power transformer, s 
is the spark gap. lj are Leyden jars, ec is the exciting coil, ac 
is an adjustment coil, aw is the aerial wire inductance coil, co 
a cut-out switch, by turning which the aerial a may be alternately 
connected to the transmitting or receiving circuits. It is designed so 
that the important circuits are open when not in use, as indicated in 
figure, cc is the counterpoise coil, cp is the counterpoise, t is the 
telephone receiver, b is a dry cell battery, vr is a variable resistance 
or potentiometer, d is a detector, c c' are capacities in the receiv¬ 
ing oscillation circuit. A head telephone is used as receiver in con¬ 
nection with a thermo-electric or electrolytic detector. 



Fig. 20.—Portable Wireless Outfit. 


The entire apparatus of a Telefunken wireless portable outfit in¬ 
cluding the mast, aerials, bicycle, generator, etc., weighs 440 pounds. 
The apparatus can be packed on 4 ponies as illustrated in the accom¬ 
panying cut, Fig. 20. The mast can be erected in 15 minutes by 5 
men. The signaling distance of this equipment overland is 40 miles. 

United States Signal Corps Portable Wireless Outfit. — This Corps 
has in service a portable wireless outfit that has given satisfactory re¬ 
sults in actual tests. The transmitting and receiving apparatus are 
placed permanently in 2 trunks. As the source of electric power for 
the primary transmitting circuit a storage battery giving 16 volts and 





124 : 


WIRELESS TELEGRAPHY. 


8 amperes is employed, or a small shunt wound generator mounted on 
a tripod and driven by 2 men by means of oppositely arranged hand 
cranks and gearing may be utilized as the source of current. The 
dynamo weighs about 100 pounds, and at 1,450 revolutions delivers 
6 amperes at 30 volts. Eight small Leyden jars are used for the 
transmitter oscillation circuit. The mast consists of 10 thin wooden 
poles 6 feet in length. Each section of pole carries a portion of the 
copper vertical wire, which is connected by suitable means as the poles 
are erected. The mast is held erect by guys insulated at intervals. 
The top section of guy wires is connected with the vertical wire, 
thereby forming an umbrella antenna. In emergencies the aerial wire 
is suspended by a King tailless kite of the box type. The kite cord, 
which serves as the aerial, consists of 42 phosphor-bronze wires woven 
over a hempen cord. The transmitting and receiving apparatus cor¬ 
respond in general to that already described herein. The entire outfit 
weighs 440 pounds and can be carried on the backs of 3 ponies. An 
important advance in portable wireless telegraphy is promised by the 
introduction of the “quenched spark” transmitter, by the use of which 
a greater range of signaling will be obtained with a reduction in the 
weight of apparatus and in the height of the aerials. 

The Clark Portable Wireless Outfit.— The Clark portable wireless 
outfit has been tested in practice and a number of sets have been sup¬ 
plied to the United States Signal Corps. The source of power for 
the transmitter is supplied by 12 storage battery cells which deliver 
approximately 4 amperes at 20 volts. A fdings coherer is used to 
operate a call bell, while a multiple steel carbon and mercury micro¬ 
phone detector is used for the reception of messages. The antenna is 
upheld by a light mast or by kites. The earth or counterpoise is ob¬ 
tained by means of a wire cloth or netting spread on the ground. The 
whole equipment weighs about 250 pounds. 


United States Signal Corps Alaskan Wireless Circuit.—This wire¬ 
less telegraph ciicuit across Norton Sound between St. Michael and 
Safety Harbor (near Nome), Alaska, a distance of 10? miles, has 
been in successful operation for several years. This wireless circuit 
is the connecting telegraph link between Nome, Alaska, and Seattle, 
Wash., the remainder of the circuit (3883 miles in all) being made 
up of 1846 miles of submarine cable and 1930 miles of land lines. 
The volume of business transmitted on this wireless circuit is over 
one million words per annum, much of which is in cipher. This 
business is handled with remarkably few errors. 



SIGNAL CORPS ALASKAN WIRELESS CIRCUIT. 125 

The station at St. Michael was designed and constructed by 
Capt. L. D. Wildman of the United States Signal Corps. An L 
antenna, supported by two masts, 200 feet high, is employed. It 
consists of 4 horizontal wires, from which 4 vertical wires separated 
by wooden spreaders lead to the operating room. The antenna may 
be lowered by means of block and tackle for the purpose of remov¬ 
ing accumulations of ice. 

For the electric power of the station an oil engine drives a 3- 
kilowatt, 500 volt, 6 ampere, 60 cycle generator. The transmit¬ 
ting key is placed in the primary circuit of the transformer, the 
contacts being broken on a bubble of mercury. The spark at the 
moment of breaking is between the edge of a hole in the upper 
contact of the maniscus of a column of mercury in the lower 
contact. With this form of key, due to Sergt. McKinney, the 
wear is inappreciable and with it 2000 words per hour have been 
transmitted in regular working. A safety device for preventing 
excessive voltages from reaching the armature of the generator 
is employed. (See U. S. patent, 764094.) An electrolytic de¬ 
tector is employed in connection with a telephone receiver of 1000 
ohms. By shunting the telephone cords with a resistance Capt. 
Wildman was able to determine the relative strength of signals in 
the receiver on different days. The greater the resistance in the 
shunt necessary in order to just hear the signals the weaker are 
the signals. By plotting a curve of the results from day to day and 
noting weather and wind conditions Captain Wildman concludes 
that wind at a high velocity when moist drives vapor particles 
against the antenna when it is highly charged, that dissipates a con¬ 
siderable portion of the charge before it can be radiated as a wave. 
The wind curves and curves of the resistance across the telephone 
rise and fall with one another. The aerial wires are utilized as a 
loop for receiving, nearly as shown in Fig. 83, page 111. To shunt 
off static electricity one leg of the antenna is so adjusted that a 
direct charge goes to earth without passing through the receiver. 

Five additional wireless telegraph stations have recently been 
constructed in Alaska by the United States Signal Corps, chiefly for 
the purpose of supplementing the land lines in this region; namely, 
at Nome (Cape Nome) 130 miles from St. Michael; Koptek, at the 
mouth of the Yukon Biver, 80 miles from St. Michael; Fort Gibbon, 
at the confluence of the Yukon and Tanana Bivers, about 300 miles 
direct from St. Michael; Fairbanks on the Tanana Biver, about 120 
miles from Fort Gibbon; Fort Egbert (Eagle City) on the Yukon, 
200 miles from Fairbanks; Circle City on the Yukon, 80 miles from 
Fairbanks and 70 miles from Fort Egbert. The station at Safety 
Harbor is to be abandoned and St. Michael will work direct with 
Nome. The antenna at these stations is supported by towers, the 
umbrella type of antenna being employed. In general the trans¬ 
mitting and receiving wireless arrangements of the United States 
Signal Corps compare practically with the best standard practice of 
the commercial companies. (See page 249.) 


CHAPTER X. 


THE BRANLY-POPP AND GUARINI WIRELESS TELEGRAPH 

SYSTEMS. 

THE BRANLY-POPP WIRELESS TELEGRAPH SYSTEM. 

This system, which is being exploited in France, is the invention 
of Professor Branly, the discoverer of the filings-coherer, and M. Vic¬ 
tor Popp of Paris. The transmitting apparatus consists of an induc¬ 
tion coil operated by a mechanical interrupter (the latter driven by a 
small motor) and the usual spark-gap. 

The most important feature of the system is perhaps a new form 
of coherer devised by M. Branly, the construction and operation of 
which are based upon the theory, confirmed by experiment, that a 
contact consisting of a polished metal and an oxidized metal consti¬ 
tute a coherer which not only possesses greater sensitiveness than the 
filings-coherer, but is also more regular in its action. 

The new Branly coherer consists of a tripod of three tapering steel 
rods r (Fig* 69), joined together at the top by a metal disk d , and with 
their feet resting lightly on a polished disk of steel s. The rods are 
composed of tempered steel which has first been given a high polish, 
and upon which a thin layer of rust has been deposited by heating 
the rods to a desired temperature in a furnace. The coherer is about 
two inches high, and is inclosed in a glass case. A lifting-screw 
(Fig. 70) is provided by which the tripod may be raised from the 
lower disk when not in use. 

Owing to the sensitiveness of the tripod coherer a very light 
tapping is sufficient to bring about decoherence, and of this fact 
M. Branly takes advantage in the general arrangement of his receiv¬ 
ing apparatus, also shown in Fig. 69. In this figure, m is the magnet 
of a Morse ink-recorder or register; l is its armature-lever, which 
carries on its right end a small platinum contact, the latter being 


BRANLY-POPP SYSTEM. 


127 


insulated from the lever. To the right of the register there is a plat¬ 
form p supported by a standard c, on which platform the coherer is 
placed, as indicated. The lever L in descending strikes a lower insu¬ 
lated stop k with sufficient force to jar the platform and thus deco¬ 
here the coherer. Normally, the lever l rests against an upper con- 
tact-stop k' } which is part of the coherer circuit, in which are also 



Fig. 69 . Branly-Popp Receiving Circuits and Coherer. 


a battery b of one volt or less, and a very sensitive polarized relay r, 
which latter operates the Morse register m by means of the lever a 
and battery V. 

The vertical wire a may be connected to the coherer and to earth 
in the manner shown, or in any other desired way. 

When arriving oscillations reach the coherer its resistance is 
reduced and relay a is operated. This in turn operates magnet m of 
the Morse register, whose armature-lever descends on k, with the 
result stated upon the coherer. It is known that decoherence takes 
place more readily when no current is flowing through the coherer. 
In this system, when the lever L starts to descend upon the post it 
first opens the coherer circuit at leaving the coherer free to deco¬ 
here when shaken or jarred. 

It is claimed that this arrangement of decohering, dispensing as it 
does with a separate decohering device, conduces to greater speed in 
the reception of signals, thirty-five words per minute having been 
taken down by this receiving apparatus. The Branly coherer is 
said to be about seven times more sensitive than the ordinary filings- 








































128 


WIRELESS TELEGRAPHY. 


coherer, which it is thought will render it well adapted to long¬ 
distance signaling. 

During the continuance of oscillations the ink-recorder prints the 
arriving signals in dots and dashes, as indicated in Fig. 70, which 
illustrates the actual appearance and arrangement of the recording 
apparatus and coherer. In this figure, m is the magnet; s is the sup¬ 
port of the paper-reel, not shown; p is the paper, which passes from 
the reel to guide-wheels, thence to an inking-disk, which is raised to 



and from the paper by means of an arm extending from the lever of 
magnet m. The paper is drawn forward by rotating drums operated 
by clockwork within the brass case of the instrument. 

It is proposed to utilize the Branly-Popp system as a means of 
distributing news from a central station in connection with branch 
offices, by masts 150 feet high placed on the tops of houses in cities; 
actual tests having shown that this is practicable for short distances. 
It is also intended to employ this system for signaling from coast 
station to coast station, and to passing ships. For the latter purpose- 
stations have been equipped at Cape de la Hague and at Cape Griz 
Nez, the mast system of which is outlined in Fig. 71. This consists 
of three masts, each 130 feet high, arranged as a triangle with sides 
130 feet in length. The vertical wires are supported by horizontal 
cables, as shown, and converge to a point R at the station, which, in 
practice, is situated at the center of the triangle. After converging 
the wires are bunched and brought into the operating-robm at v. A 




























































GUARINI SYSTEM. 


129 


five horse-power gasoline motor is employed to drive a dynamo which 
charges a storage battery used for the induction coil and other purposes. 

These two stations will, it is 
expected, cover a distance extend¬ 
ing westward over 900 miles. It is 
intended to exchange messages with 


other stations and vessels equipped 
with the Slaby-Arco and Marconi 
systems, a syntonizing system de¬ 
vised by M. Branly being capable 
of receiving different wave-lengths. 

The details of this syntonic system 
are not yet available. 

For the purpose of obtaining 
news from the races, or in case of 
accidents at points ten or twenty 
miles from the city, an automobile 
of special construction, in which 
a wireless outfit is placed, is em¬ 
ployed. To support the aerial wire 
a high bamboo mast braced by wires 
and placed in a socket on the roof of the vehicle is used. The neces¬ 
sary current is supplied by a storage battery kept charged by a small 
dynamo driven by a gasoline motor in the automobile. 



Fig. 71 . 

Branly-Popp Aerial Wires. 


THE GUARINI WIRELESS TELEGRAPH AND RELAYING SYSTEM. 

Marconi in his first experiments with wireless telegraphy endeav¬ 
ored to direct the electric waves in one direction by the use of a 
metallic reflector, but this was not found to be necessary in practice. 

M. Guarini has devised a method by which more than one message 
may be sent or received from opposite directions simultaneously with¬ 
out resorting to syntony. Taking advantage of the fact that conduc¬ 
tors are opaque to electric waves of high frequency, he employs a 
long metallic tube terminating in a metallic cylinder with a slot in one 
side. The tube consists of a sheathed cable 57 feet long; the cylin¬ 
der is 33 feet long, diameter 1.6 feet. The vertical wire proper is 
carried within the tube or cylinder and connects with the transmitting 
and receiving apparatus. The cylinders, etc., are supported from 























130 


WIRELESS TELEGRAPHY. 


towers and monuments as indicated in Fig. 72, in which also s repre¬ 
sents the slotted cylinder, s' the slot, and c the conductor. 

In operation the slot is placed oppo¬ 
site the place to which a message is to 
be sent or from which one is to be re¬ 
ceived. The incoming waves that fall 
upon the conductor through the slot set 
up oscillations that affect the coherer. 
The oscillations set up in the sheathing 
are diverted to earth, to which the 
sheathing is connected. Reversely, in 
transmitting signals waves are emitted 
through the slot only, and hence are 
radiated in the direction in which the slot may be faced. 

Guarini’s Relaying System.—M. Guarini has also devised a 
method of repeating or relaying messages by wireless telegraphy. His 
experiments were made between Brussels and Antwerp, a distance of 
about 26 miles, with relaying apparatus about midway, namely, at 
Malines (Mechlin). The relaying is effected by practically the same 
method as that first employed by Morse, who caused the armature 
of a receiving instrument at a repeating or intermediate station 
to relay a message from, say, a southerly station, x, to a northerly 
station, Y. Analogously, Guarini causes the armature-lever of a 
relay controlled by the coherer relay at a repeating station to operate 
the primary circuit of the oscillator, whereby a message is relayed 
from one station to another. 

The theoretical connections of this arrangement are shown in 
Fig. 73, in which for clearness some of the shunt coils and the tapper 
are omitted, b is a metallically sheathed box somewhat like that 
used by Marconi and for the same purpose. In this box are placed 
the coherer transformer t, condenser c, relay r, etc. The repeat¬ 
ing relay r', controlled by relay R, is placed outside of the box b. In 
the receiving position of the armature-lever l of repeating relay r', 
the aerial wire a is connected to the primary coil p of transformer t. 
In the transmitting position the same lever closes the primary cir¬ 
cuit x x of the oscillator I, the secondary of which is attached to the 
spark-balls in the usual way. Hence, when a signal is received at the 
intermediate station from, say, station x, the coherer is operated, 
with the result that relays r and r' are also operated. This closes 












GUARINI RELAYING SYSTEM. 


131 


the primary circuit x x of oscillator coil i, and the signal is trans¬ 
mitted to station Y. Instantly the coherer is decohered by the tap¬ 
per, relay r is again connected with aerial wire A ready to receive 
other signals from station x, and so on; it being understood that 
these actions of the relays take place in a very brief space of time, 
approximately .01 second, in order to properly transmit the signals. 



As the repeating relay r' is not limited as to current by which it 
may be operated, and as a large space is required between its sending 
and receiving contacts, the armature-lever of the instrument is of 
special construction, and the relay itself with its armature is sup¬ 
ported on two well-insulated cylinders. The lever is of metal and is 
about twelve inches long. It is divided into three parts, each part 
being insulated from the other by hard rubber. One part carries the 
vertical-wire contact, the middle part holds the armature of the relay, 
the third part carries the induction-coil current and contact of the 
primary wire. 

The induction coil I used by Guarini at the repeating station 
gives a 10-inch spark, with a current of 3 amperes and 30 volts, it 
having been found that a stronger current quickly impaired the con¬ 
tact-points of the repeating relay r\ The condenser in the secondary 
of t effects two purposes—breaking the continuity and modifying the 
capacity of the circuit, according to the inventor. 

To avoid the formation of arcs between the filings of the coherer 
itself (similar to “frying” in the telephone transmitter), due to an 
excess of current in that instrument, whereby the filings would self- 
cohere, Guarini employs a resistance coil r of 2000 ohms, which is 







































132 


WIRELESS TELEGRAPHY. 


normally short-circuited at contact a of relay R, but when a is open 
that resistance is thrown into the circuit of the coherer, ftelay r is 
sensitive to a current of 20^00 ampere; its resistance is 1100 ohms. 
It is of the polarized type. The condenser o', according to Guarini, 
is employed to diminish the normal length of the spark, thus to 
lessen the travel of the armature of relay r'. The coherer employed 
by Guarini is of the Blondel regenerable type, described subsequently. 
The resistance of the primary wire of transformer t is about .75 ohm, 
that of the secondary wire s, 11000 ohms; the resistance and induct¬ 
ance of spool J n n are 40 ohms and 35 henrys respectively. The coil j 


is used to exclude extraneous waves from the coherer. 

By the arrangement of the induction coil t used in the receiver 
circuit the effects of atmospheric electricity are obviated. At the 
terminal stations of this repeating system an induction coil and 
mechanical interrupter are employed, but the oscillator and spark- 
gap are dispensed with, the secondary wire being connected in series 
with the aerial wire and earth respectively. Hence the waves radiated 
thereby are of comparatively low frequency, unless, perhaps, the 
surgings in the induction coil noticed by Bernstein may have some 
effect in the transmission. 



Fig. 74 . Blondel Coherer. 

The Blondel Regenerable Co¬ 
herer.—This coherer is outlined 
in Fig. 74. c c are conductor 
plugs separated by a space of about 
.2 inch and between which are 
placed fine filings &, which are 
made of a mixture or alloy of 
oxidizable with non-oxidizable 
metals, such as silver with nickel 
or copper, pp is formed of an 

amalgam paste which hardens in a short time and makes a joint with 
the stoppers s s. The tube is made of glass and is exhausted of air. 



Fig. 75 . 






























DUCRETET-POPPOFF WIRELESS TELEGRAPH. 


133 


It has an extension u projecting from a point over the filings in the 
tube. Additional filings k are placed in the bulb u', and by this 
means the amount of filings in the tube proper may be added to, or r 
if necessary, reduced. 

This coherer and tapper are shown in Fig. 75 as arranged in prac¬ 
tice by M. Guarini. k is the Blondel coherer, upheld by supports n; 
t is an electro-mechanical tapper; s is a spring by which the angle 
of t, and hence the position of the striker h relative to the coherer, 
may be adjusted. To guard the coherer from injury the ends of the 
tube are inclosed in copper sleeves which butt against the leading-in 
wires. The sleeves slip between the openings at s s, and are held in 
that position by suitable screws. 


THE DUCRETET-POPOFF WIRELESS TELEGRAPH. 

M. Ducretet, alone and jointly with M. Popoff, has devised 
several variations of transmitting and receiving wireless apparatus. 
With his earlier apparatus M. Ducretet transmitted signals to Eiffel 
Tower, Paris, from a distance of three or four miles, using the ordi- 



Fig. 76. 



Fig. 77 . 


nary oscillator, filings-coherer, vertical wire, etc. The type of trans- 
mitting-key used is shown in Fig. 76. In this the contact is broken in 
mercury contained in a suitable vessel. A rotary mercury interrupter 
is employed for the primary current of the induction coil. 













134 


WIRELESS TELEGRAPHY. 


In Fig. 77 is outlined the receiving apparatus and circuits used 
in the later arrangement of this system. A vertical wire terminating 
in a metallic cage k is upheld by suitable supports. A telephone t 
is utilized as receiver; h is an auto-coherer of the carbon type; 
n n are induction coils in the coherer circuit; b is a small battery. 
With this apparatus signals have been transmitted a distance of about 
60 miles over water. 

As previously remarked, Popolf was perhaps the first to utilize 
the coherer in connection with a vertical wire, the arrangement of 
coherer, relay, and tapper being practically as appears in Fig. 12, 
except that the aerial wire and ground are not there shown. Several 
different types of coherers were used by M. Popoff in the experi¬ 
ments relating to the detection of electrical vibrations. One consists 
of two strips of platinum foil pasted on the inside of a glass tube. 
One strip of the foil is brought out to the external surface at one end 
of the tube, the other strip to the opposite end. The tube is placed 
horizontally with the platinum strips in the lower portion of the tube, 
the powdered filings resting on the strips and covering them. The 
tube is about half filled with the filings. The most satisfactory 
results were obtained with iron filings. Powdered antimony and 
small bird-shot were also used in the coherer. 


CHAPTER XI. 

THE DE FOREST WIRELESS TELEGRAPH SYSTEM. 

DE FOREST UNTUNED SYSTEM. 

This system, due to Dr. Lee De Forest, of New York, is in 
successful operation in a large number of places in the United States 
and Canada. From the first the object of the inventor has been to 
eliminate as far as possible every feature of the conventional wireless 
apparatus that is liable to introduce trouble more or less frequently 
in the ordinary course of operation, with the result that the De Forest 
system is noted for its simplicity and freedom from complicated 
apparatus. 

Thus the usual induction-coil generator is replaced by a motor- 
driven dynamo machine, and interrupters of all sorts are dispensed 
with. The filings-coherer, tapper, and relay are replaced in the 
De Forest system by a detector of electric waves termed a “ re¬ 
sponder, ” and a telephone-receiver, while the typical wireless trans¬ 
mitting key of cumbrous proportions is in this system supplanted 
by the ordinary Morse key used in wire telegraphy in this country. 

One arrangement of the transmitting and receiving circuits and 
apparatus of the De Forest untuned system is shown in Fig. 78. 
In the figure, A is the vertical wire, which is permanently connected 
to the oscillator circuit and may be connected to the receiving circuit 
and apparatus of the system at will by means of the switch svv; w is 
a spring-jack by which the receiving apparatus may, when desired, 
be entirely disconnected from the transmitter and aerial wire ; c' is 
an oil or gas engine used, where steam power or an electric motor is 
not available, to drive the alternating-current generator D. (In Fig. 80, 
the generator d is attached to the same shaft as an electric motor c\ by 
which the generator is rotated. This device is termed a motor-genera¬ 
tor. The motor receives its current from any available source.) The 


136 


WIRELESS TELEGRAPHY. 


capacity of the generator varies from one to forty or fifty kilowatts at 
500 volts, according to the distance to be signaled over, e, Fig. 78, 
is a small direct-current dynamo or exciter used to excite the magnetic 
field of the generator; m is a magnetic choke-coil of 5 ohms resistance, 
in the circuit of the generator and primary of a choke-transformer U. 



Fig. 78 . De Forest Transmitting and Receiving Circuits. 


The choke-coil m is supplied with a core of soft-iron wires, the number 
of which may readily be varied when it is desired to increase or decrease 
the current strength for the purpose of fattening or thinning the 
spark at the discharge-gap s. The transformer u has a ratio of trans¬ 
formation of unity. Its function is to prevent the high potentials 
generated in the step-up transformer T from jumping through to the 
armature of D. The transformer t raises the voltage of the circuit to 
25,000 or 50,000 volts. Spiral choke-coils pc, about five inches in 
diameter, composed of 22 feet of No. 11 B. and S. insulated copper 
wire, wound spirally, as indicated, are placed in the circuit between 
the secondary of T and the spark-gap s, for the purpose of confining 
the rapid oscillations set up by the oscillating circuit to the vertical 
wire A. The gap is shunted by four or six quart Leyden jars L, forming 
an oscillating circuit. The capacity of such jars is about .003 micro¬ 
farad, but varies somewhat according to the thickness of the glass. 
They are in this instance connected in series multiple as indicated, 
that is, two sets of three jars in series connected in multiple, which 
gives a total capacity of about .0045 microfarad. These Leyden jars 
are charged by transformer T, and, as described elsewhere, set up 
oscillations of high frequency when the spark-gap breaks down under 
the high potentials of the transformer. In other words, they store 
up electric energy during the time that the electromotive force is 
rising to the breaking-down point at the spark-gap, which energy is 






















DE FOREST DISK SPARK-GAP. 


137 


dissipated in establishing oscillations in the antennae that are radiated 
as electric waves. This energy is comparatively small. Fleming 
gives the energy thus stored up as . 1 foot-pound in a vertical wire 
150 feet long, having a capacity of .0003 microfarad, and in which 
the potential at the spark-gap is about 30,000 volts. Several differ¬ 
ent forms of sparking devices are used by De Forest. In one type 
two brass arrow-head points or straight points, with a metal disk 
between them, are used (see Fig. 86). In another form, shown 
separately in Fig. 79, three aluminum disks a b c are utilized. 
These disks are about 1.5 inch in diameter and about .25 inch thick. 
They are made up of strips of aluminum wound spirally to provide a 
large surface for heat radiation, and are separated by an air-space of 
.25 inch to .65 inch. Disks a and c are upheld in a vertical position 




Fig. 80 . Motor-Generator. 


by corrugated ebonite supports 6 6\ the middle disk b is suppoited 
by a brass rod v from the insulated stand or base B. I he outei 
disks ct c are connected to the oscillator ciicuit s L and to the veitical 
wire A respectively, as shown in the preceding figuie, constituting, 
with the spark-gap, a closed oscillating circuit which discharges into 
the vertical wire or wires. To secure syntony between the condenser 
circuit and vertical wire an inductance may be introduced in series 
with the two sets of Leyden jars, or the capacity may be varied. To 
deaden the noise of the discharges at the spark-gap the sparking-disks 
are sometimes inclosed in a sound-proof box. In the operation of the 
one-kilowatt machines, however, the noise is not disturbing. In 
Fig. 80 L is a box containing the Leyden jars, and s is the spark-gap. 

& Key K is placed in the primary circuit of transformer T, Fig. 78, 
and, as superficially observed, is an ordinary Morse key, but it 
does not directly break the circuit. It does so, howevei, indirectly 



























138 


WIRELESS TELEGRAPHY. 


by means of a projecting arm which normally rests on a strip 
key c immersed in oil in a box b. When the key is depressed it 
causes strip c to close the primary circuit of t. When it is raised 
the said circuit is opened. It is occasionally found after this contact- 
breaker has been operated for some time under oil that pure carbon 
is deposited on the contact-points, but this is not detrimental. For 
comparatively short distance signaling, that is, for instance, with the 
one-kilowatt generator, it is not found necessary to open the transmit¬ 
ting key under oil. With this type of key, shown on its baseboard, 
Fig. 86, the speed of signaling is equal to that at which signals are 
transmitted on land lines, say 25 to 30 words per minute, the make 
and break of the spark following every move of the transmitting key. 
(The writer has himself transmitted signals at approximately the lower 
rate mentioned by this key.) Similarly, the auto-coherer responds to 
every break in the continuity of the oscillations, the signals being 
received as a succession of short and long sounds in the telephone. 

The arrangement of receiving circuits shown to the right of 
switch sw in Fig. 78 is designed for a single vertical wire (see Fig. 83). 
The coherers, when in operation, are in series with the vertical wire. 
Two responders R R are shown, either of which may be cut in or 
out of circuit by the two-point switches s' s' in the event of one or 




Fig. 82. Calling Relay. 


other getting out of adjustment. A battery b of three cells and two 
pairs of head telephones t are in shunt with the responder r. By 
means of shunt-switch s one or more cells may be placed in service. 
Other variations of the De Forest receiving circuits are outlined in 
Figs. 81 and 82. In the former the telephone t is in series with a 
















































MULTIPLE AERIAL WIRES. 


139 


condenser of about half a microfarad capacity, and both are shunted 
by a resistance r of about 5000 ohms, which is regulable according to 
requirements. In Fig. 82 three responders R are indicated. These 
can be put in circuit or not, as desired, by switches s. R is a sensi¬ 
tive relay used as a call or ‘ 4 step-up” signaling device to operate t' y 
which may be a bell or other suitable device easily operated by bat¬ 
tery b. By means of switch s' head telephones 11 are interchangeable 
with relay r'. More or less battery may be introduced into the 
coherer circuit by suitable manipulation of switch s. 

De Forest uses two types of anti-coherers, one of which, termed 
in shop phrase the “ goo ” responder, is electrolytic in its action; the 
other is a “needle” anti-coherer, both will be described. 

Another and later arrangement of the De Forest transmitting and 
receiving circuits is shown 
in Fig. 83. In this, A 
represents the antennae. 

Vertical wires a b are me¬ 
tallically connected at the 
top. They are brought to 
small metal balls x x! re¬ 
spectively. These balls are 
opposite a larger ball y, 
from which they are sepa¬ 
rated by an air-space of 
about one thirty-second of 
an inch. The larger ball 
is connected to the trans¬ 
mitting circuit, as shown, 
s being the spark-gap, t the 
step-up transformer, and 
L the Leyden jars. The receiving circuits are attached to the 
balls x x'. In this arrangement it may be seen the wires a b of 
the antennae have separate routes to earth, one passing through a 
responder r', the other via responder R and a small condenser c. 
On the other hand, the responders are in series with each other, 
with telephone t, battery b', and wires a b. Thus the joint effect 
of both responders, due to received oscillations set up by the incoming 
waves in the vertical wires, is obtained in the telephone circuit. 
When “static” currents, due to atmospheric electricity, are preva- 



Fig. 83. 


De Forest Multiple Aerial Wire 
System of Circuits. 






























140 


WIRELESS TELEGRAPHY. 


lent, the responder r' is short circuited, or nearly so, by the switch s 
and a resistance not shown, this affording a direct path to earth for 
such currents, the condenser c assisting in this diversion, while the 
oscillations continue to pass through responder r and condenser c to 
earth, sw is the cut-out switch. 

When a large number of vertical wires are used, one of them, a , 
is brought to ball x , as shown, the others, indicated by dotted lines, 
are connected to ball x' . It is found in practice that the short air- 
gap at x x' y has very little, if any, damping effect on the transmitted 
oscillations. 

De Forest Anti-Coherers or Responders. —The De Forest elec¬ 
trolytic anti-coherer is shown as R in Fig. 84, which figure repre¬ 
sents an early arrangement of the De 
Forest receiving system. This de¬ 
tector is an anti-coherer, inasmuch 
as its resistance increases under the 
influence of electric oscillations, and 
was invented by Dr. De Forest and 
Mr. E. II. Smythe. It is based on 
the fact that certain electrolytes 
separating two metal electrodes be¬ 
come conducting when a direct cur- 
De Forest Electrolytic Coherer, rent is set up in the circuit. A 

microscopic examination shows this 
to be due to an action in which metallic particles are detached 
from the positive electrode and deposited on the negative, until a 
“bridge” or threads of such particles reaches from one electrode to 
the other. When a suitable electrolyte is chosen, it is found that an 
oscillating current disrupts this bridge and thereby renders the elec¬ 
trolyte non-conducting. The substance used by the inventors con¬ 
sists of equal parts of fine filings of tin and oxide of lead formed 
into a sort of paste by vaseline or glycerine with a small amount of 
water or alcohol added. This is placed in a space e' between metal 
rods e e in a suitable tube h. In operation, when a current from 
battery b alone is flowing, these filings build up bridges which close 
the gap, electrically considered; but when electric oscillations are set 
up in the circuit, disruptive electrolysis takes place with a mild 
explosive generation of hydrogen gas, which destroys the bridges, 
thereby largely increasing the resistance of the circuit. On the cessa- 



r -B 

4vw\mvh|i|— 


Fig. 84. 













DE FOREST AUTO-COHERERS OR RESPONDERS. 


141 


tion of the oscillations the bridges at once reform automatically under 
the influence of battery b. The variations in the strength of current 
thus produced affect the receiver H, which may be any suitably sensi¬ 
tive instrument; but, in practice, head telephones are employed, as 
indicated in other figures. This responder is very sensitive, and, in 
consequence, the current strength required in the telephone circuit 
is very low, about one six-thousandth of an ampere, and it will 
respond accurately to the waves set up by a spark one sixty-fourth 
inch long, forty feet distant, with a metal wing two feet long, and 
without ground connection, n n are the usual inductances or choke- 
•coils that may be employed to force the oscillations through the 
■coherer circuit. In fact, however, the responders used in this system 
have, relatively considered, so little resistance the choke-coils are not 
required in practice, r is an adjustable resistance of perhaps 5000 
ohms, to regulate the current strength furnished by the battery b to 
.suit the requirements of the coherer. (See Appendix, p. 303.) 



Fig. 85. De Forest Needle Coherer and Circuits. 

The De Forest needle anti-coherer, known as type No. 3, is sim¬ 
plicity itself. It consists of a steel needle n, Fig. 85, upheld against 
two aluminum rods a a by a retractile spring s attached to the needle, 
.as indicated, the pressure of needle n against the rods being regulated 
by the winding-screw s'. The rods are part of the usual coherer cir¬ 
cuit, and the responder is connected as shown at r r', Fig. 83. A 
film of oil and moisture held between the needle and aluminum 
makes the device an anti-coherer, but its resistance is varied by the 
oscillations, thus giving the characteristic signals in the telephone. 
The sound set up by this responder somewhat resembles that induced 
in a telephone whose circuit is adjacent to a direct-current dynamo 
circuit, but more uniform, this sound being broken into long and 
short intervals—that is, dots and dashes. 


















142 


WIRELESS TELEGRAPHY. 


In Fig. 86 is outlined a shipboard outfit of this system, showing 
the principal transmitting and receiving apparatus, s is the spark- 
gap; sw is a double-throw switch; K is the key on the box B con¬ 
taining the circuit-breaker; R R are the anti-coherers, and t the 



Fig. 86. Shipboard Outfit. 


head telephones; L is the box containing the Leyden jars. This 
figure virtually illustrates the arrangement of the De Forest appa¬ 
ratus in the cabin of the steam-yacht Erin during the international 
yacht races of 1903. a represents the wires leading to the antennae. 
These consist of five No. 14 wires, stranded and insulated with rub¬ 
ber. These wires are strung taut and are kept six inches apart by 
spreaders. A special topmast gives a height of 120 feet from the 
roof insulator at the cabin to the yard peak. To supply necessary 
current a one-kilowatt alternating-current generator is belted direct 
to the dynamo engines of the yacht. This current is carried by 
special wires to the switch s', thence to the transformer, not shown. 

THE DE FOREST SYNTONIC SYSTEM. 

The bulk of the success achieved by the De Forest system for the 
first three or four years of its existence has been obtained by the 
untuned system just described, which has been found ample for the 
distances to which it has been applied. Dr. De Forest, in common 
with other workers in this field, has recognized that for long-distance 
operations it is necessary to avail of the well-known advantages of 
syntony, and has worked out a number of syntonic methods, for 
which he has recently obtained several patents, amongst others U. S. 
patent No. 730,246. 

The De Forest tuned circuits are based upon the principle involved 
in what is known as the Lecher system of wires, namely, that when 
















































DE FOREST SYNTONIC SYSTEM. 


143 


two parallel adjacent wires of equal length, such as are shown in 
hig. 87, are connected to the terminals of an apparatus or oscillating 
system T capable of producing oscillations of high frequency, if the 
wire is one quarter, or any 

a b y 2 \ c /4Ai) 


multiple of one quarter 
the wave-length of the os¬ 
cillations, the waves will 
be reflected from the ends 
of the wire. 


gr 


t b 

Fig. 87. Lecher System of Wires. 


Such a system of wires is assumed to be distortionless—that is, the 
inductance and capacity, being uniformly distributed, cancel each 
other—hence the waves undergo no attenuation, and stationary or 
standing waves due to the incident and reflected oscillations are set 
up in the system. The velocity of propagation of the weaves in such a 
system will equal that of light when the resistance of the wires as 
compared with the inductance may be neglected, and when the 
inductance is the reciprocal of the capacity per unit length. These 
conditions will exist when the diameter of the wire does not exceed 
.019 inch and when its length is less than 328 feet. 

In such a system, as De Forest and others point out, the capacity 
and the inductance cancel each other so far as the dimensions of the 
wire are concerned, and the period of vibration is independent of the 
diameters of the wires or of the distance by which they are separated. 
At any corresponding point of the two parallel wires the charges in 
them will be of exactly equal potential, but of opposite phase, that 
is, one will be positive, the other negative, while the currents in the 
wires will be in opposite directions at any corresponding point. As, 
however, the current differs in phase by one-quarter wave-length 
from the potential, the latter will be at maximum where the electro¬ 
magnetic energy or current is zero, and vice versa. 

If, then, sections ab and bc are one-half wave-length, the points 
b and c will be nodes, while d will be a loop of electrostatic energy. 
On the other hand, b and c will be loops and D a node of electro¬ 
magnetic energy. Hence, as the maximum difference of potential 
exists at a loop of electrostatic energy, a coherer which is operated 
by electrostatic forces can be advantageously placed across d, while 
a detector responsive to current variations, like the De Forest 
responder, can be placed to advantage across the wires at c. (For a 
mechanical illustration of loops and nodes, see Fig. 52.) 





144 


WIRELESS TELEGRAPHY. 


Bridges b b , consisting of short pieces of wire, may be inserted 
between the two wires at b, c, or the wires may be grounded at 
those points without affecting the oscillations; in fact, if the wires 
be grounded at such points they will act beneficially in diverting all 
waves to earth that are not tuned to the period of the system. 

In untuned wireless systems, as already noted, the oscillations are 
rapidly damped, consisting perhaps of two or three swings, and thus 
the effect upon the receiving instrument is not as great as would be 
a longer train of weaker waves. According to De Forest, he has 
found the Lecher system of wires an excellent resonant vibrator, 
having a very marked period of its own, and being but little respon¬ 
sive to waves that do not correspond to its own rate of vibration. 
Further, inasmuch as most of the lines of force lie in the space 
between the two conductors, it is a poor radiator of waves, and hence 
it is a persistent vibrator, continuing to vibrate for some time after 
the oscillations have been set up, in this way producing a long wave- 
train, which is slowly damped. By reason, also, of the ability to set 
up stationary waves higher potentials are obtainable. Inasmuch as 
the velocity of propagation in a simple Lecher system is equal to that, 
of light, the frequency or wave-lengths may be readily determined. 
The system may thus be accurately attuned to any desired frequency,, 
and as the nodes and loops of the stationary waves are fixedly located, 
connections may be made with the wires at any phase of the wave 
desired. 

Since, as stated, it is a feature of the Lecher system of wires that 
the period of vibration is independent of the size of the wires or of 
the distance between their centers, the period of any section of such 
a system embraced between any two consecutive bridges, as b b r 
depends altogether upon the distance or length between such bridges. 
It is known that the mutual induction of such wires is diminished as 

they are brought nearer 


A 


C 


"L 


Fig. 88. 


— together, while the capac¬ 
ity of the wires increases 
correspondingly. Hence, 
if, as in Fig. 88, the wires 
of one section (ab) of such a system, equivalent to half a wave-length, be 
brought close together, it will possess comparatively high capacity and 
little inductance, whereas the further separated wires of section bc, also 
half a wave-length long, will have low capacity and high inductance. 







DE FOREST TUNING METHOD. 


145 


1 he product of the inductance and capacity in each section will, how¬ 
ever, be the same, but in the case of ab the electrostatic energy will 
be in excess, while in bc the electromagnetic energy will predominate. 
Thus, when two opposite charges pass from ab, in which the capacity 
is large and consequently the difference of potential is low, to bc, in 
which the capacity is small, the difference of potential is thereby 
increased, since it is well known that for a given charge in a con¬ 
ductor the potential is inversely proportional to the capacity. (A 
mechanical illustration of this effect may be offered: Suppose a gas- 
meter to hold a cubic foot of gas at a certain pressure; if the size of 
the meter be diminished by say one half, the amount of gas remaining 
the same, the pressure will be doubled.) Reversely, when two oppo¬ 
site charges pass from a section of low capacity to one of high capacity 
the electromagnetic energy is enhanced while the difference of poten¬ 
tial is diminished. This system, therefore, provides a means of 
transforming oscillations from high to low potential and low to high 
electromagnetic energy. 

In the application of these principles to practice, however, it 
would not always be convenient to separate the wires to obtain low 
capacity, nor would it be feasible in every case to extend the wires to 
the wave-length of the oscillations. De Forest has therefore adopted 
the plan of twisting to¬ 
gether the wires of each 
section,as shown in Fig. 89, 
using insulated wires, his 
experience having shown 
that wires so arranged possess the characteristics of the Lecher system. 
Furthermore, this arrangement permits the wires to be wound in a coil 
on a spool, thus providing a portable device. To avoid induction 
between adjacent convolutions of the wires, De Forest states they 
should be laid with a pitch of at least three turns to the inch on a 
spool three inches in diameter, with successive turns separated by an 
eighth of an inch; but the use of the coils is not limited to the fore¬ 
going proportions. 

In Fig. 89 the wires of a receiving circuit are shown extended in 
a straight line from the vertical wire a to the detector r. Here the 
detector is at the loop of an electrostatic wave, n n are choke-coils,. 
V is a local battery, and t is a telephone or other suitable receiver.. 
It will be seen that the wires in the quarter-wave section b are morn 







146 


WIRELESS TELEGRAPHY. 


widely separated than in the half-wave section A. This separation 
may be secured by using thicker insulation on one section than on the 
other. A bridge b and condenser c are placed across the wires, as 
shown, for the purpose of increasing the lag or to adjust the period 
of the system. To facilitate such adjustment the bridge is adapted 
to make connection at any desired part of the wires by means of a 
clip to which is attached two needle-points capable of perforating the 
insulating material. 

Another means by which De Forest secures greater capacity in 
the wires is by immersing one section of the wires in oil, which has 
a higher specific inductive capacity than air. Of course, also, the 
methods of securing syntony or variations in the wave-lengths by 
this means are not limited to the methods described, inductance being 
used in some instances, etc. 

In Fig. 90 is shown an application of the Lecher wires to a send¬ 
ing circuit, p s are the primary and secondary coils of an induction 
coil or transformer t; s is the spark-gap; c is a condenser; b is a 
section having a half wave-length, and connected to the vertical wire 
as indicated. The electrical energy is stored in the condenser c until 
the potential exceeds the breaking-down strength of the spark-gap, 
when oscillations are set up in section B, part of the energy of which 
is reflected back at «, forming stationary waves with nodes of poten¬ 
tial at those points, and part of which enters the vertical wire. 


\A 


AA. 


CO 


J= , £ 


c T/M F 


Fig. 90. 


U 


CO 


BE 




Fig. 91. 


In another arrangement of the transmitting circuits the Lecher 
system is charged inductively, the secondary circuit of the transformer 
or induction coil being in circuit with the said system and oscillating 
with it. In still another arrangement of transmitting circuits, Fig. 91, 
the Lecher system, section b, is so disposed as to have one-quarter 
wave-length, the secondary coil of the transformer T being equivalent 
to one-half wave-length, in which case the point a , Fig. 8, would 
be a loop of potential. It is, however, preferable always to connect 
the antenna to a node in the parallel conductors, a is the vertical 
wire, grounded through the parallel conductors. Condenser c at the 











DE FOREST WIRELESS TELEGRAPH STATIONS. 147 

left is the bridge or tuning condenser; c c at the right are the spark- 
gap condensers. 

This method of electrical tuning has been used very successfully 
in tests between Washington and Annapolis, and its use is to be 
extended on the De Forest system. Besides the close and accurate 
tuning which this method gives, it possesses the further advantage 
that it is not affected by outside interference; De Forest has found 
that the period of the ordinary helix or coil used in tuning is easily 
disturbed by the proximity of masses of iron, or even by the approach 
of the hand. 

De Forest Wireless Telegraph Stations. —The De Forest Wire¬ 
less Telegraph Company already have in operation or under con¬ 
struction over twenty stations in the United States and Canada. 
Among these, New York City to Fort Hancock, 12 miles; Block 
Island to Point Judith, 15 miles; Toronto to Hamilton, Canada, 40 
miles; Buffalo, N. Y., to Cleveland, Ohio, 180 miles; Cleveland, 
Ohio, to Detroit, Mich., 150 miles; Block Island to Cape Hatteras, 
300 miles. Also between Chicago and St. Louis, about 300 miles 
overland. 

Perhaps the most important work contemplated and under way is 
a circuit that will extend from Cape Flattery, Wash., at the junction 
of Strait San Juan de Fuca and the Pacific Ocean, to Dutch Harbor, 
Aleutian Islands, a distance of about 1800 miles. For these stations 
three latticed and girded wooden towers, each 225 feet high, and 
arranged as a triangle, with sides 275 feet long, are being constructed. 
The towers will be 25 feet square at the base. From the top of these 
towers a hexagonal net of cable will be strung horizontally, from 
which will hang six screens of vertical wires having an average length 
of 250 feet, 300 wires in all. These wires will converge into the 
station located at the base of the towers. The station-house will be 
equipped with a 90 horse-power steam-engine, a 60-kilowatt genera¬ 
tor, transformers, etc. 

The Cape Hatteras equipment consists of a single tower, 200 feet 
high and 23 feet square at base. The station-house is located between 
the four legs of the tower. The antennae consist of 40 vertical 
wires suspended from the top of the tower and fastened to a bus bar 
at the base of the tower and carefully insulated therefrom. The 
power employed at the station is about 15 kilowatts. From this 


148 


WIRELESS TELEGRAPHY. 


station it js contemplated to communicate with Block Island and 
Havana, the latter 400 miles distant. 

At Buffalo, Cleveland, and Detroit stations two masts, each 200 
feet high and 100 feet apart, are being erected. The plane of these 

masts is faced in the direction of trans¬ 
mission of the signals. A horizontal cable 
between the mastheads susjiends 20 ver¬ 
tical wires which converge in the station- 
house. Each of these vertical wires is com¬ 
posed of seven No. 21 B. and S. bare tinned 
wire, stranded. The power employed 
at these stations is about 7.5 kilowatts.. 
The arrangement of these masts, vertical 
wires, and station is outlined in Fig. 91. 

The arrangement of the Point Judith 
or Providence Journal vertical wires is; 
outlined in Fig. 92. Here five vertical 
wires a a, supported by a mast 150 feet, 
in height, are employed. 

The wires are held apart 
by wooden spreaders s' s'. 

The arrangement at the 
base of the wires is a slight 
variation of that shown 
in Fig. 83, wires w w leading to the receiving circuits, 
and s being the spark-gap. 

For some time a number of automobiles have been 
fitted out with De Forest apparatus, and have been 
utilized in New York City as a means of transmitting 
items of stock news from the street into the offices 
of the Wall Street Journal. The vehicle carries a 
large glass case about three feet square, in which the 
apparatus is placed. A brass rod about seven feet 
high serves as the vertical wire. The oscillations are set up by a 
two-inch spark induction coil supplied by the storage battery, of the 
vehicle. 

The author is under obligations to Dr. De Forest for his courtesy 
in supplying many of the foregoing details of his system. 



RANG EM ENT FOR 20 W]RES. 






































CHAPTER XII. 


THE FESSENDEN, STONE, SHOEMAKER, MASSIE AND MUSSO 

SYSTEMS. 

THE FESSENDEN SYNTONIC WIRELESS TELEGRAPH. 

The inventor of this system, Professor R. A. Fessenden, has car, 
ried on a multiplicity of experiments in wireless telegraphy in this 
country under the auspices of the United States Weather Bureau, 
and has made many notable discoveries and improvements in the 
art, for which a large number of patents have been issued. 

Professor Fessenden has also made numerous practical experiments, 
some of which are described, relative to electric wave propagation, 
concerning which he states his belief that the waves radiated from 
the antennae are not complete waves, but only half-waves, which 
travel over the surface of a conductor, and thus, unlike Hertz waves, 
can be deflected from a straight line. He found that for the proper 
transmission and reception of these waves it was essential that the 
surface at the base of the vertical wire should be a good conductor for 
a distance of at least a quarter of 
the wave-length from the foot of 
the vertical wire. He therefore de¬ 
vised the arrangement shown in 
Fig. 94, which he terms a wave- 
chute, to effect this result. It con¬ 
sists of the vertical wire A supported 
bv a mast, in this case on the top 
of a building. From the foot of A, 
a conductor h h , properly insulated, 
is led over the housetops, horizontally, to the required distance, and 
in the direction in which signals are to be transmitted, before ground- 



Fessenden’s Wave-Chute. 















150 


WIRELESS TELEGRAPHY. 


ing. To prevent absorption of wave energy by the iron guy wires, 
coils x x are added thereto, this giving them a different oscillation 
period to that of the antennae. 

In actual practice the Fessenden system has been in successful 
operation between several places—for instance, from Cob Point, Md., 
to Arlington, Va., a distance of 47 miles overland. This country is 
open, but well wooded with trees of considerable height. Professor 
Fessenden states that the strength of signals is varied to a marked 
degree by the temperature of the earth. Thus, measurements made 
during the prevalence of warm weather showed the signals to be 
seven times stronger than when the ground was frozen to a depth 
of several inches. 



The transmitting and receiving circuits of one arrangement of this 
system are shown theoretically in Fig. 95. This is a tuned system. 
The tuning device employed is termed a tuning-grid, and consists of 
a combined inductance and capacity, made up of one or more pairs of 
parallel wires, which, to reduce their inductance, are bent back and 
forth, in box D, and to increase their capacity are immersed in oil 
(see Fig. 96). A is the vertical wire or wires. 

















































































FESSENDEN WIRELESS TELEGRAPH. 


151 


In the practical operation of this system each station is allotted a 
certain oscillation period, as an ordinary Morse station would he 
allotted a certain letter of the alphabet. Normally, the receiving 
apparatus of each station is attuned to its given period of oscillation. 
Hence, when it is desired to call any station, a succession of waves of 
the proper frequency are transmitted from the sending station with 
the result desired. The transmitting circuit may be traced from A 
to the secondary of inductance coil I (or other source of oscillations), 
or to the spark-gap s', thence to and through the wires w w of the 
tuning-grid d, thence to earth, s is a switch by which the primary 
of induction coil I is opened when signals are to be received; b is 
the battery for the induction coil. It also operates, as required, 
solenoids n n '. This system may be operated by opening and closing 
the primary of induction coil in the usual way, but the inventor 
prefers to keep the coil in continuous operation, and to transmit 
signals by short-circuiting or varying the tuning device d, which 
throws the sending circuit out of tune with the receiving circuit. 

To effect this short-circuiting of d, a key K is employed, with 
fingers /, which fingers, when the key is depressed, touch one or other 
of the wires w w in succession. By this arrangement, at each closing 
of key k a series of oscillations of different periods are transmitted, 
any one of which the receiving station may select at will. Hence, if 
the receiving station considers that he is being interfered with by an 
outside station with one oscillation period, he can attune his receiving 
circuit to another of the oscillation periods being transmitted. The 
capacity and inductance of the wires w in box d can be varied by 
moans of the movable contacts c c , which are arranged to be moved 
along the wires w w in tuning the transmitting circuit, and in a 
practically similar way the receiving circuit may be attuned at d'. 

The receiving circuit may be traced from aerial wires a to con¬ 
denser c, to the combined capacity and inductance grid d', to the 
detector k (an auto or self-restoring detector), to the grid d, and to 
earth, all in series, t is a head telephone in a shunt circuit 1 , 2, from 
the detector k\ and in series, via resistance r, with a battery V of two 
cells of slightly different voltage, arranged in opposition to each other. 

The inventor of this system has devised a number of different 
types of detectors. The one k, shown in the ecompanying figure, 
is termed by him the “ barretter. ” It is based on the well-known 
fact that the resistance of a metal conductor varies with the tempera- 


152 


WIRELESS TELEGRAPHY. 


ture of the metal, and the construction of the barretter is accordingly 
designed to give rapid increments and decrements of temperature 
with increase and decrease of current in its circuit, thereby to obtain 
comparatively large variations of resistance in the circuit. The bar¬ 
retter is shown separately at the upper left corner of the figure. It 
consists of a very short, thin silver wire, having a core of platinum p. 
This wire is made from a very short silver wire .1 inch in diameter 
with a platinum core .003 inch in diameter. This wire is then drawn 
until it has an outside diameter of .002 inch, in which case the plati¬ 
num wire will be .00006 inch thick. The wire is then formed into a 
loop. From a very small portion of this loop (a few hundredths of 
an inch) the silver is dissolved by immersion in nitric acid. The 
loop is then connected to platinum leading-in wires as shown. To 
avoid heat radiation, the loop is inclosed in a glass bulb s' about one 
inch long and one-half inch wide, filled with air or paraffin; or the 
bulb may be exhausted of air with a very considerable increase in 
sensitiveness. To further avoid the radiation of heat, the loop is 
inclosed in a very small silver shell g , suitably upheld. 

The sensitiveness of the loop in this respect is further increased 
if only a portion of the silver wire composing the loop be dissolved, 
in order to obtain a composite wire with half the resistance of the 
platinum wire. This, according to the inventor, can best be done 
by removing all of the silver wire and then recoating the platinum 
wire with silver until the resistance of the loop is just one half that 
of the platinum alone. 

This gain in sensitiveness is due to the fact that as the silver has 
one seventh the volume of platinum, and equal resistance, a given 
amount of current will heat the silver wire approximately seven times 
as hot as the platinum wire, thus bringing about a greater variation 
in the resistance with a given current. The resistance of the loop is 
in some instances as low as 30 ohms, while others less sensitive vary 
from 150 to 600 ohms. The importance of a low resistance detector 
in syntonic wireless telegraphy has already been pointed out. 

Owing to the slight difference in potential between the cells V , a 
very weak current normally passes through the loop. When the cur¬ 
rents due to the received electromagnetic waves traverse the loop l , 
they cause rapid increases in its temperature and consequently in 
its resistance, which results in a series of sounds in the telephone 
receiver t, which sounds are received as dots and dashes of a code. 


FESSENDEN DETECTOR. 


153 


This type of detector or auto-coherer differs from the filings-coherer 
in that in the latter the reduction in resistance is primarily due to the 
electromotive forces of the received oscillations, while the increased 
resistance of the former is primarily due to the currents set up by 
the received oscillations. A number of detectors of different degrees 
•of sensitiveness may be grouped in the receptacle h, and means bo 
provided for changing quickly from one to the other. 

For calling purposes a less sensitive detector or loop is used, and 
in addition a microphone transmitter m with battery and induction 
coil i is placed opposite the diaphragm of the telephone receiver T, with 
the result that the sound is heard in the calling receiver t'. At other 
times a galvanometer or telephone is used for calling without the 
microphone contact, a is a lightning arrester, which, by means of 
switch s and the solenoid n, is put in service when the apparatus is 
set for receiving, and opened when the switch is set for sending. 
Somewhat similarly, the detector apparatus is detached from the ver¬ 
tical wire when switch s is set for sending, by the solenoid n' and the 
lever in the manner outlined in the figure. The condenser c pre¬ 
vents the effects of atmospheric steady currents upon the detector 
when connected with the vertical wire, but repeats or transmits the 
received oscillating currents. 

By means of clockwork, indicated at switch s, mechanism can be 
set in operation whereby at stated periods of one minute, more or 
less, the switch s may be thrown from sending to receiving auto¬ 
matically, when a station is not busy. Other stations listening in and 
hearing this regular signal know that the desired station is available, 
and proceed to call him. This automatic device is cut off when the 
station is busy. 

The lightning arrester a consists of a Varley carbon coherer, or 
preferably a gold-bismuth filings-coherer, made of an alloy of gold 
and bismuth, with five per cent, of bismuth, placed in a glass tube 
and lying between electrodes tipped with an alloy of platinum-iridium. 
Still another device for this purpose is described, consisting of a small 
ring of aluminum and silver, resting on a knife-edge of gold-bismuth 
alloy, a' is an inductance coil across which any static charge from 
the antennae leaks to ground. 

The transmitting key used in this- system is shown in Fig. 9G. 
K is an ordinary Morse key mounted on a suitable base. The exten¬ 
sion f, when depressed by the key, causes the fingers / (Fig. 95) to 


154 


WIRELESS TELEGRAPHY. 


impinge against the wires or strips 6, in the manner and for the pur¬ 
pose stated. D is the box containing the wires 5 and the movable 

contacts 6. These contacts arc 
grooved wheels upheld by the bars 
s s , the wires or strips 5 resting 
in the grooves; o represents the 
oil in which the wires are im¬ 
mersed; 9 are adjusting arms by 
which the bars s are held in a 
desired position. 

Besides the foregoing, a large 
number of variations of this system 
and apparatus are described in 
U. S. patents Nos. 706,735 to 706,747, to which the reader may be 
referred for a more detailed account of Professor Fessenden’s work 
in almost every branch of this subject. 



Fig 96. 

Fessenden Transmitting Key. 


THE STOKE MULTIPLEX SYKTOKIC WIRELESS TELEGRAPH. 

A large number of patents have been issued to the inventor of this 
system, Mr. John Stone Stone, of Boston. The general purpose of his 
inventions may be briefly described by an extract from U. S. patent 
714,831, in which he claims a system for developing free or unguided 
simple harmonic electromagnetic signal waves of a definite frequency 
to the exclusion of the energy of signal waves of other frequencies, 
and an elevated conductor and means for developing therein forced 
simple electric vibrations of corresponding frequency. In a system for 
receiving the energy of free or unguided simple harmonic electromag¬ 
netic signal waves of a definite frequency to the exclusion of the energy 
of signal waves of other frequencies, he claims an elevated conductor 
and a resonant circuit associated with said conductor and attuned to 
the frequency of the waves, the energy of which is to be received. 

From the many diagrams which accompany the specifications, the 
one shown in Fig. 97 may be selected. This represents a tuned selec¬ 
tive multiplex system, the sending apparatus being shown on the left, 
the receiving apparatus on the right, x represents a receiving system 
tuned to respond to transmitting system x'; y is a receiving system 
tuned to respond to transmitting system y'; c are condensers, and l 
are inductances employed to secure the desired rate of oscillations in 
























STONE MULTIPLEX SYNTONIC SYSTEM. 


155 


the respective circuits, k k are transmitting keys; w w are circuit 
interrupters in the primary of inductance coil i, and c'c'are the con¬ 
densers used therewith; tt are transformers or induction coils; 
h k are coherers, decohered by tappers not shown in figure; R R are 
relays. To avoid repetition, it may be considered that the operation 
of the transmitting circuits is somewhat similar to that of the Flem¬ 
ing transmitting circuit previously described (Fig. 38). It will be 
observed that systems x' and y' are both connected to the same ver¬ 
tical wire a 7 ; also that the receiving circuits x Y are likewise con¬ 
nected to one vertical wire A. Receiving system x, being attuned to 
transmitting system x', will only respond to signals therefrom. Simi- 



Fig. 97. Stone Multiplex Syntonic System. 


larly, system y will only respond to signals from y'. As previously 
remarked (p. 52), if it is found feasible to secure sufficiently accurate 
tuning, such arrangements should be found practicable, and need not 
be limited to two sets of signals. 

The oscillating circuits a a of the transmitting systems x' are 
attuned to the same period, the object of employing circuit a being 
to “weed ” out any harmonic vibrations that may have been developed 
in circuit a\ thereby screening the vertical wire from such harmonics. 
This screening action of the interposed circuit «, as the inventor 
notes, is due to the property which such a resonant circuit possesses of 
opposing the development in it of other frequencies than that to which 
it is attuned, while it favors the development of the simple harmonic 
currents of the period to which it is attuned. Similarly, oscillating- 
circuits b V of transmitting system y' are tuned to a like period, but 
of course different from the period of x , for the purpose described. 
Likewise, also, in the receiving systems, the circuit a corresponds in 















































156 


WIRELESS TELEGRAPHY. 


frequency to a', and b to b ', to screen the detector circuits from any 
waves that may not be in tune with the vibrations assigned to the re¬ 
spective circuits. The inventor does not limit the number of screen¬ 
ing circuits to one, but adds as many inductively connected as may 
be required. In the operation of such multiple systems, to which 
there are analogous a number of well-known systems in wire teleg¬ 
raphy, the different frequencies will be superposed on the vertical 
wire, which in such cases should be arranged as an aperiodic vibrator, 
the respective receiving circuits in each case selecting the train of 
waves to which they are attuned. 

The Stone Wireless System has undergone a number of modifica- 
tions since the foregoing remarks concerning it were written, as may 
be observed by reference to Fig. 97 a, in which is outlined the present 
arrangement of circuits and apparatus of a 10-kilowatt installation of 
this system. The transmitting circuits and apparatus are shown to 
the right of the vertical dotted lines; the receiving circuits and ap¬ 
paratus to the left thereof. 

One of the new features of this system is a multiple grouping of 
the transmitter inductance and capacity. Thus the transmitter oscil¬ 
lation circuit is inductively coupled to the aerial a by means of 4 or 
more spiral open oscillation transformers t', the primaries p and sec¬ 
ondaries s' of which are connected in multiple, as shown, one ter¬ 
minal of each secondary coil being connected through a “loading” or 
inductance coil l to the aerial, its other terminal going to earth e 
direct if relay r' is closed, or to earth at e, via the primary receiv¬ 
ing circuit a i c if that relay is open, as will be more fully described 
presently. The oscillation transformers (t') are arranged in a circle 
on a table, the secondary on top of the primary coils, as indicated. 
Each coil contains 10 or 12 turns of heavy copper, the diameter of 
coil being about 9 inches. In a communication to the author Mr. 
Stone notes that according to his experience the multiple arrange¬ 
ment of these circuits is the only way in which a spark telegraph sta¬ 
tion of high power can be made to radiate waves as short as 400 
meters at full power of the station and with one spark for each half 
cycle (alternation) of the generator. He also finds that this multiple 
arrangement serves (as theory indicates) to make the wave trains 
radiated very much more persistent than when a single condenser and 
inductance coil are employed. 



HIGH POWER CIRCUITS. 


157 


Another feature of the Stone system is the method employed in 
transmitting the Morse signals. This consists in opening and closing 
the secondary circuit of the step up power transformer, or induction 
coil, t, by means of a series of contacts k at a multiple “break” b, 
operated jointly by an electromagnet m (or separately by individual 
electromagnets, not shown), the coils of which are in series in a 110 
volt, 1 ampere circuit, in which is placed a telegraph key k'. This 
device is utilized to avoid the arcing and burning of contacts in the 
heavy current primary circuit of the transformer. Eight contacts, 
each l /% inch in length, are outlined in the figure; 8 more similar con¬ 
tacts might be inserted if desired, as indicated at x. In the figure g 
is a 10-kilowatt motor generator developing 110 volts at 60 cycles, 
c' c' are condensers, cj represents small spark gaps, and f f are fuses 
(protective devices) in the primary circuit of a closed core oil in¬ 
sulated power transformer t with primary and secondary coils p s. 



b' is an adjustable resistance in that circuit. The spark gap in the 
oscillation circuit consists of a number of brass rods sg in parallel, 
one or more of which may be cut out as desired, c c, etc., are the 
usual condensers in the oscillation circuit, one for each primary of the 
oscillation transformer t'. These condensers are of the plate glass, 
tin foil type, immersed in oil, to avoid brush discharges around the 
edges of the foil. V V are “loading impedance” coils. 

The transmitting and receiving circuits of this system are 
arranged to give the operator an opportunity of listening for 
interruptions from the distant station between his own sig¬ 
nals. This is done by giving the key k' control of the break 
magnet m, and also of two 4-ohm pony relays r r', all in the 
same local circuit, as shown. The act of closing key k' closes the 
magnet and the relays. The closing of magnet m closes the sec¬ 
ondary circuit of transformer t at the multiple contacts k of break b ; 
































158 


WIRELESS TELEGRAPHY. 


the closing of relay r' places the aerial to earth at e via the armature 
contact n ', and also short circuits a i c at n'. At the same time the 
circuit of detector d is opened at the armature contact n of relay r. 
When the key is opened the transmitter oscillation circuit is broken 
at the contacts k of break b, and the armatures of the relays r r' 
fall to their back stop or contact, closing the detector circuit at n 
and placing the primary receiving circuit a i c in the aerial circuit 
through the multiple secondaries s' of the oscillation transformer t', 
and a loading or tuning coil Z. Thus during each opening of key k 
the operator has an opportunity to hear interruptions. 

In Fig. 97 a primary, secondary and tertiary receiving circuits are 
shown. The secondary circuit, c e i' x is the weeding out circuit which 
is used, as in the figure, when great selectivity is desired, and when 
wave lengths of 200 to 600 meters are employed. When the greatest 
selectivity is not required, and using the same wave lengths, the weed¬ 
ing out, or secondary, circuit is cut out by placing the double throw 
switches x y to the right and closing small switch z. For wave lengths 
of 600 to 1,000 meters the switch z is opened, x, y remaining as be¬ 
fore. For waves from 1,000 to 2,000 meters x is turned to the left, y 
to the right, z open, q is a potentiometer, controlling small battery 
5. t is a head telephone receiver, d is the detector, c c c' are variable 
condensers in the receiver circuit, for tuning purposes, a is an ad¬ 
justable tuning coil. This coil is 2 inches in diameter and has about 
135 turns of No. 20 wire, 20 turns to the inch. The coil i of the pri¬ 
mary receiving circuit is also 2 inches in diameter and consists of 33 
turns of No. 20 wire, 20 turns to an inch. Each coil e i' of the weed¬ 
ing out circuit consists of 30 No. 36 enamel covered copper wires, 
stranded, 24 feet in length and wound on a spool 1.5 inch diameter, 
in .25 inch channel. The tertiary coil e' consists of 30 feet of 30 No. 
36 copper wires, stranded, and enamel covered, on a spool 2 inches in 
diameter, .5 inch channel. All B and S gauge. 

In low power installations of the Stone system a specially con¬ 
structed telegraph key is employed, by means of which the receiving 
and transmitting circuits are alternately connected with the aerial 
wire in practically the same manner as this operation is performed 
by key k and relays r r', Fig. 97 a. The arrangement is shown in 
Fig. 975. In this case only one primary p and one secondary s' of the 
oscillation transformer are employed. Otherwise the transmitter cir¬ 
cuits are the same as in Fig. 97 a. In Fig. 975 the coils of transformer 


STONE SYSTEM CIRCUITS. 


159 


t are shown connected to earth, as is sometimes done to meet particu¬ 
lar conditions of certain installations. In the receiving system a i is 
the primary; e V is the weeding out circuit; e' c' is the tertiary cir¬ 
cuit. These circuits are provided with switches, not shown in this 
figure, corresponding to x y. Fig. 97a. When the telegraph key k 



is open, as in Fig. 975, the apparatus is set for receiving; the contact 
at the right hand end of key being broken, this placing the aerial to 
ground through coil a and primary i. At the same time the detector 
circuit is closed and the primary of the power transformer t is open 
at the left end of the key. When key k is closed these conditions are 
reversed. These devices dispense with the need of the ordinary anchor 
gap and throw over switches described in connection with some other 
systems. 

The detector used in the Stone system is outlined at d Fig. 975. It 
consists of 2 small glass tubes, one containing a fine platinum wire, 
the other a small piece of platinum foil; the lower ends dipping into a 
dilute solution of sulphuric acid contained in a small phial. External 
connection with the fine wire and foil is made by means of mercury in 
the upper part of the tubes and by wires leading therefrom. A small 
battery 5 and potentiometer and the usual head telephone t are used 
with the detector. 

In the Stone system the power transformer t is for some installa¬ 
tions designed to give unity power factor in the primary with the spe¬ 
cial oscillation condenser used. In other installations, as at the 
Brooklyn Navy Yard, high power installation, a power factor loading 
coil, or a power factor condenser, or both, are included in the second¬ 
ary of the transformer for the same purpose. This is a 15-kilowatt 
closed core transformer in oil insulation. 







































160 


WIRELESS TELEGRAPHY. 


In the said Brooklyn Navy Yard installation of the Stone s} stern 
power is supplied by a 110 volt, 60 cycle, 15-kilowatt motor generator. 
In this installation a 48 contact “break” device, each contact ]/% inch 
in length, is employed in the high potential or secondary circuit of 
the transformer. There are 8 multiple transmitter oscillation circuits 
at this station, each corresponding to c p s' Tig. 97 a, and three re¬ 
ceiving circuits each corresponding to a b c in Fig. 97c. In Fig. 97c 
three receiving circuits 1, 2, 3 are shown connected to the aerial for 



simultaneous triplex receiving, a is the aerial, l is the loading coil 
and s the secondaries of the oscillation transformers t' of Fig. 97&. 
r' is the pony relay, set for receiving, a represents the primary, b, the 
secondary, or weeding out circuit; c the tertiary of the respective re¬ 
ceiving circuits 1, 2, 3. According to Mr. Stone 3 messages have been 
received simultaneously at the Brooklyn Navy Yard installation by 
means of this arrangement of circuits, one from a station at Cape 
Cod, another from the Government station at Fire Island, and the 
third from a ship in New York Harbor. Each of these multiple cir¬ 
cuits is of course tuned to the wave length of the desired incoming 
signals. There are numerous installations of the Stone system in 
United States Navy Yards and on battleships. 


THE SHOEMAKER WIRELESS TELEGRAPH SYSTEM. 

The devices due to H. Shoemaker cover a wide range of circuits 
and apparatus for wireless telegraphy. 

One of the earlier arrangements by Mr. Shoemaker is an oscillator 
consisting of two halls connected with the usual induction coil. These 
balls are separated by two other balls, the latter within a box con¬ 
taining a gas dielectric under high pressure. This arrangement, it 
















SHOEMAKER WIRELESS SYSTEM. 


1G1 


is claimed, obviates the retardation of sparking under oil. The 
coherer used with this system consists of a tube in which are contained 
the filings. Immediately above the filings a small iron ball is placed 
in a suitable receptacle. Above the ball is the pole-piece of a magnet 
controlled by the relay in the coherer circuit. The movement of this 
ball within the tube when acted upon by the .magnet suffices to deco¬ 
here the filings. 

Another device by Mr. Shoemaker consists of a receiver which 
comprises a plurality of plates in inductive relation to one another, and 
means for permanently charging such plates, together with a micro¬ 
phone circuit operated by the plates. 

Mr. Shoemaker has also designed a wireless telegraph repeater 
consisting of a detector aud a relay controlled thereby; a circuit 
controlled by the relay which insulates the coherer and simultaneously 
closes the circuit; also means for restoring the coherer and for the 
generation of retransmitted energy. See U. S. patent No. 718,535. 

Mr. Shoemaker’s most important practical work, however, has been 
done in connection with the International Wireless Telegraph Com¬ 
pany, the transmitting and receiving circuits of which are shown theo¬ 
retically in Fig. 98m The transmitting circuits are shown at the left, 
the receiving circuits at the right of the figure. The radiant energy 
is primarily set up by a generator D developing 110 volts, which are 
raised to 25,000 volts by transformer T. This E. M. F. charges a 
capacity c, which discharges into the closed oscillating circuit s, c, l, 
and thence into the aerial wires A a', of which there may be two or 
more (not joined at the top), via small arcing spaces b' b, about .03 inch 
apart, similar to those shown in the De Forest system (Fig. 83). 

Mr. Shoemaker finds that much depends on the form of energy 
transmitted, and has obtained best results with large capacity c and 
small inductance L. The capacity C consists of a number of large 
Leyden jars, arranged in multiple. These jars are described in Chap¬ 
ter XIV. The inductance L is in series with the antennae. It con¬ 
sists of five turns of .25-inch copper tubing, 15 inches in diameter, 
wound around the side of a drum or reel formed of two thick pieces 
of mahogany, which are held apart by bars of ebonite 6 inches in 
length. The tubing rests in notches in the ebonite bars, and each 
turn is separated by an air space of one inch. The discharge-rods, 
which are adjustable, are in the center of the reel, the spark-gap 


1G2 


WIRELESS TELEGRAPHY. 


being in the middle of the reel. The adjustable contact, indicated by 
the arrow-head, is fixed laterally but is movable vertically. The reel is 
revolvable, and the adjustment is obtained by turning the reel around 
until the desired inductance is obtained. In practice about 2.5 turns 
of the tubing are used. The transmitting circuit may be detached 
from the receiving circuits by a suitable switching arrangement x, 
which is inclosed within the box containing the detector. The receiv¬ 
ing apparatus is also separated from the transmitting system by the 
small air-gaps b V. The fact that in systems employing tuned oscil¬ 
lating circuits the potential at the foot of the vertical wire is virtually 
zero, is found to render extra precautions as to insulation at this point 
not so requisite. This would follow from Hertz’s dumb-bell oscillator 
experiments. For an opposite reason, it may be remarked, thorough 
insulation toward and at the top of the wire is very necessary, the 
maximum potential being there. The key k is of the Morse type, 



Fig. 9 8 a . Shoemaker Transmitting and Receiving Circuits. 


but somewhat larger than the ordinary, and is provided with heavy 
platinum contact-points, which are opened in air. Auxiliary carbon 
contact-points attached to the key were tested, but were not found 
to possess any advantage. 

The detector employed in this system is microphonic in its charac¬ 
ter, and is self-righting. It is indicated at B in Fig. 98m In the 
figure, //are small pieces of incandescent-lamp filaments laid across 
steel knife-edges e e. The filaments are about 1.5 inches in length and 

































































MUSSO SYNCHRONOUS SYSTEM. 


1G3 


are- highly elastic. Firm contact between the filaments and the steel 
edges is secured by means of a fine strip of hard rubber r r, which is 
pressed down upon the filaments by a spring n, the tension of which 
is easily regulated. There are four sets of filaments, three filaments 
in a set. It will be seen that each set of filaments is in series with 
the others and with a battery of four dry cells b' and telephonic 
receiver t. The filaments are in series with the vertical wires and 
earth through small condensers c c c, as shown, the oscillations being 
more or less diverted to this route by the inductances l' l'. The 
tuning or adjustment at the receiving station is effected by adjusta- 
able inductances l' l' and the capacities c c c, which, it will be ob¬ 
served, have a closed oscillating circuit through the detector. Each 
condenser is formed of three sheets of tin-foil about 1.5 inches long 
and . 88 inch wide, separated by very thin sheets of mica. According 
to tests made, the capacity of these condensers is .0045 microfarad 
each. The inductances l' l' are formed of 350 feet of No. 16 cop¬ 
per wire wound spirally on a bobbin ten inches long and four inches 
in diameter, and are adjustable by a sliding contact as indicated. In 
the adjustment of this detector it is found that best results are 
obtained by increasing the tension on the filaments for near-by sig¬ 
nals and decreasing the tension for remote signals. When necessary 
to further vary the wave-length the vertical wires A a' are lengthened 
out by the insertion of additional wire in the operating-room. Signals 
have been received by this detector at a distance of 140 miles, and it 
is in daily operation between Quogue, Long Island, and Highlands of 
the Navesink, New Jersey, a distance of 90 miles. 


A more recent arrangement of the Shoemaker system is outlined 
Figs. 98&, 98e\ Here G is a motor driven, 1 kilowatt, 110 volt, 120 
cycle generator, t is an open core power transformer analogous to 
that described pages 202, 203. (See also Chapter XIV.) / is an in¬ 
ductance adjustable to obtain resonance with the oscillation circuit, 
c represents a battery of 20 Leyden jars or tubes in 2 series of 10 each. 
These tubes are 16 inches high by 2 inches in diameter, and are cop¬ 
per coated to within 4 inches of top. The capacity of each jar is 
.0150 microfarad: total capacity in multiple series .0075 microfarad. 



164 


WIRELESS TELEGRAPHY. 


For land installations of 5 kilowatts and over hydro-condensers are 
employed in this system, consisting of plain glass jars or tubes, 16 
inches by 2 inches, inserted in a close-fitting brass tube, and for the 
inner plate having a metal cylinder of suitable size, the space between 
the inner cylinder and the jaw being filled with plain or acidulated 
water. These jars are arranged in batteries of 63 tubes, in multiple 
series of 21 tubes; capacity of each series approximately .090 micro¬ 
farad; total capacity .030 microfarad. These condensers are not 
adapted to shipboard use owing to the rolling of the vessel, l is the 
usual transmitter tuning inductance helix, practically similar to l 
Fig. 98a. The spark rods r r are of brass and are tubular. A current 
of air is forced through the tubes for cooling purposes and to remove 
the ionized air at the spark gap. s is a double pole, double throw 
“lightning” switch for placing the aerial directly to earth, cutting out 



all apparatus, as in the figure, during lightning storms, a is an 
anchor gap. A is a looped aerial, v is a variable tuning condenser of 
.005 microfarad in the aerial receiving circuit, v' is a tuning con¬ 
denser in the receiving oscillation circuit, variable from zero to .001, 
.002 or .003 microfarad, c is a fixed condenser of .001 to .003 micro¬ 
farad, the chief function of which is to avoid short-circuiting the 
telephone receiver t via the tuning coil V. s' s' are parts of a throw 
over switch, more or less common to all wireless systems, bv means of 
which the transmitting and receiving circuits are kept electrically 
apart. In the figure the system is set for receiving, therefore the pri¬ 
mary circuit of the power transformer t is open at s', k is a Morse 
key w 7 hich opens the primary circuit directly without injurious spark¬ 
ing on low power plants. For installations of 10 or 15 kilowatts the 
transmitting device in Fig. 98c is utilized. This consists of differ- 
































SHOEMAKER CIRCUITS. 


165 


entially wound coils a a', b b', in the arm b of which the key k is in¬ 
serted. When the key is open the impedance of coil V reduces the 
current flow below the breaking-down point of the spark gap. When 
the key is closed the impedance of each coil is neutralized by that of 
the other coil and the maximum current flows. An advantage of this 
device is that the key opens a circuit in which the current strength is 
small. For instance, in Fig. 98c, if the normal current output is 100 
amperes the current flowing in coils a and a' will be 50 amperes; in 
coils b b', 25 amperes. A high resistance rheostat r, shunted across 
key k, is found to eliminate sparking at its contacts. Some curious 
characteristics of this device have been noted by Mr. Shoemaker, due 
apparently to auto transformer effects. For instance, with the key 
open, the measured E. M. F. across a' is 110 volts, across coil a 220 
volts, across b' 220 volts and across kev k 440 volts. 

The Shoemaker detector consists of a small zinc rod and a fine 
platinum wire dipping into a dilute solution of sulphuric acid con¬ 
tained in a small cup and is the equivalent in some respects of a 
small primary battery. The fine platinum wire is sealed in a small 
glass tube. For convenience of handling a cover is provided in the 
cup through holes in which the zinc rod and the glass tube pass down 
into the electrolyte. Connections to the oscillation circuit are made 
by clamps on the cover of the cup. The glass point of the platinum 
wire should be immersed about yVinch in the solution. 

In operation, if the arriving signals become feeble it is probably 
due to the burning of the fine wire of the detector by strong oscilla¬ 
tions from nearby powerful stations, or by heavy atmospheric dis¬ 
charges, a very common occurrence with fine wire detectors. When 
this occurs the glass point should be removed from the cup that the 
point may be rubbed down by means of a small whetstone provided 
for the purpose, until the wire is again level with the end of the glass 
tube, beyond which the wire need not project. The wire should be 
kept scrupulously free of dirt and grease. The zinc rod should be 
kept well amalgamated with mercury, for which purpose it should be 
removed, cleansed, and if necessary re-amalgamated every two or three 
days. No extraneous battery is required with this detector, which is 
quite sensitive. It is now used in place of the steel carbon detector 
shown in Fig. 98a, in the installations of the Shoemaker system. 

There are now about 70 land and shipboard installations of the 
Shoemaker system in various parts of the world, ranging in power 
from 1 kilowatt to 10 kilowatts. 


166 


WIRELESS TELEGRAPHY. 


THE MASSIE WIRELESS TELEGRAPH SYSTEM. 

This system, due to Mr. Walter W. Massie, is installed on a num¬ 
ber of the steamboats plying between New York City and Fall River, 
Mass.; Providence, R. I.; New London and New Haven, Conn. There 
are also commercial stations outfitted with the Massie system at Block 
Island, R. I.; Point Judith, R. I.; Wilson Point, Conn.; Cape May, 
N. J., and elsewhere. The United States Navy and the United States 
Signal Corps have also obtained a number of sets for use at shore 
stations. 

The transmitting and receiving apparatus and circuits of this sys¬ 
tem are indicated diagramatically in Figs. 1, 2, 3. In Fig. 1 a is the 
vertical wire, a is an anchor gap. (See page 139.) s is the spark 
gap which is contained in a micanite case, in which there is a small 
window, through which the spark may be seen. An inductance coil 
is wound spirally on a frame around the micanite case (Fig. 6). The 



Figs, i, 2, 3.—Massie Transmitting and Receiving Circuits. 


inductance is varied as desired for tuning by moving the clips or 
wedges c ' c\ The usual capacity c of the oscillation circuit consists 
of a number of glass plates covered with tin foil. (Fig. 6.) The 
power transformer t is supplied with 60 cycle current at 110 volts, 
from a motor generator g, which are transformed to 40,000 volts at 
the secondary terminals. The power of the Massie stations varies 
from 2.5 kilowatts, or less, to 15 kilowatts, depending on the signaling 
distance to be covered, k is a transmitting key of the Morse tele¬ 
graph type, used directly in the primary circuit of low power stations. 
In high power stations, to avoid burning out the contacts, the key is 
caused to operate magnetically an oil switch in the primary of the 
transformer circuit; not shown. 









































STEEL-CARBON DETECTOR. 


167 


To avoid heating at the spark gap of the transmitter the spark 
rods r, r, Fig. 1, are made of copper tubing and air is forced through 
them; the expansive action of the air cooling the terminals of the rods. 
Further, the air removes the heated and ionized air from the vicinity 
of the gap, thereby conducing to greater steadiness in the operation 
of the spark gap. The expanded air is allowed to escape through the 
tubular inductance coil, thereby reducing its temperature and increas¬ 
ing its efficiency. The compressed air is admitted to the spark rods 
and to the inductance coils by needle valves. 

In Fig. 2 is outlined the apparatus intended for an alarm or call 
circuit. The detector k is a sensitive filings coherer; r is the usual 
relay, b is battery for tapper t and call bell d, V is coherer battery. 
s s' are small switches. Condensers and resistances (not shown) to 
prevent sparking at the relays and other contacts are employed. 

Fig. 3 represents the apparatus and arrangement of circuits em¬ 
ployed in receiving regular messages. A microphone detector d, de- 



Fig. 4 .—Filings Coherer. Fig. 5.—Steel-Carbon Detector. 


scribed subsequently, is connected in series with the aerial in the figure. 
A variable condenser c and inductance l constitute the tuning ap¬ 
paratus. A telephone t wound to 1,500 ohms, and local battery b 
are in shunt with the detector, s' is a small switch to open and close 
the telephone circuit when desired; the current strength in this circuit 
is regulated by resistance r r. 

The Massie filings coherer is shown separately in Fig. 4. m is a 
flexible brass strip supporting a glass tube g and a silver-lined cup c, 
within the tube, w is a magnetized needle whose lower end extends 
to the filings. It is held in a given position by the screw s. The 
needle forms part of the coherer oscillation circuit. The iron filings 
are upheld by the attractive force of the needle, and are normally sep¬ 
arated by a film of air from the mass of the non-magnetic filings in 



























108 


WIRELESS TELEGRAPHY. 


the cup. This general arrangement appears to facilitate the cohering 
and decohering of the filings by providing a short path for the oscilla¬ 
tion currents over the surface of the filings to the lining of the cup. 
Hence the entire mass of the filings is not cohered, but only the sur¬ 
face filings. The filings are decohered by the tapper t which jars the 
supporting strip m. The resistance of this coherer ranges from 50 
ohms normal to 1 ohm when cohered, thereby making it feasible to 
employ a low resistance and comparatively inexpensive relay. 

In Fig. 5 is shown the Massie steel-carbon coherer termed the os- 
cillophone. A steel needle rests on carbon blocks c c (a compound of 
carbon and paraffin) with knife edges, held in niches on an insulating 
base b by metal strips s s, which also electrically connect the carbons 



Figs. 6, 7.—Massie Transmitting Apparatus and Controlling Switch. 

with the binding screws b b. A horseshoe magnet m holds the needle 
firmly against the non-metallic posts n n, thereby preventing the 
needle from sliding or rolling off the carbons. The resistance from 
binding post to binding post of this microphonic detector is normally 
about 40,000 ohms, which falls to 1,000 ohms, when oscillations are 
received. It decoheres automatically. 

As it is known that the tuning of a circuit is varied more or less by 
a changeable resistance in the oscillation circuit which a microphonic 
detector introduces, a detector of the magnetic type in which the re¬ 
sistance is small and fixed has been used in some of the installations 
of the Massie system. 






MUSSO SYSTEM. 


169 


The plate condensers referred to are shown in Fig. 6, within the 
frame F, on which are placed the spark gap and inductance coil l. 
The number of plates in use may be varied by means of the plugs or 
clips ft. To prevent or diminish the losses due to brush discharge 
around the edges of the plates, so much of the glass as is not covered 
with the foil is painted with an asphaltum varnish. 

Normallv the filings coherer is connected with the vertical wire to 
receive incoming calls. Hence it is not necessary for the operator 
to hold the telephone receiver to his ear continuously. When a call 
is received the microphone detector is switched into the circuit and 
the filings coherer is cut out. Also when it is desired to transmit a 
message, both of the detector circuits are switched out and then the 
transmitting circuit only is connected with the aerial. These switch¬ 
ing operations are performed by moving the handle h of a controlling 
switch s, Fig. 7, the contacts of which are so designed that it is not 
possible to connect either of the receiving circuits with the other or 
with the transmitting circuit at the one time. 


THE MUSSO SYNCHRONOUS SYSTEM. 

This system, the invention of Signor Guisippe Musso, is a syn¬ 
chronous telegraph system, designed primarily to be operated by and 
in connection with wireless telegraph apparatus. It consists essen¬ 
tially of a fly wdieel or disk at a transmitting station, in the manner 
common to other synchronous telegraph systems. Usually, however, 
such other systems transmit signals by the Morse dot-and-dash 
method, or, if letters are printed at the receiving station, they 



170 


WIRELESS TELEGRAPHY. 


are printed on a strip of paper—not altogether a satisfactory method 
for public use. In the Musso system it is intended to print the mes¬ 
sage in page form. The principle of this synchronous system is not 
difficult to understand. 

A fly-wheel w, Fig. 98, carried on shaft s and rotated by clock¬ 
work gearing, indicated at s', is arranged at each station. Below this 
wheel is a stationary liard-rubber disk d. A pair of copper rings c c 



to' 

Fig. 98. Musso Synchronous System. 


are inserted on the surface of the rubber. Holes h li are placed at 
regular intervals around these rings, one for each key, on a keyboard. 
From these rings, as indicated, wires w w lead to the primary p of the 
oscillator circuit. On the under side of the fly-wheel a metal wedge v 
is carried. This wedge is wide enough to span the space between 
rings c c , but does not touch them. When a given key k of the key¬ 
board is depressed, its lever l, with its arms a a , which latter are drawn 
toward each other by a spring s', is raised. The hook ends of the 
arms pass through the holes and are held in that position until wedge v 
arrives over them, when it passes between the hooks, separating them 
so that they fall below the rings c c, being withdrawn by spring s. At 
the same time the metal wedge, by contact with the metal hooks 
of a a , had closed the oscillator circuit, permitting oscillations to pass 
to the aerial wire A. So much for the transmitting arrangement. 

The receiving system is attached to the same disk and fly-wheel. 
Two other copper rings c' c' are arranged around the disk. These are 
connected by wires w' w' with the armature-lever of coherer relay r. 
A pair of brushes b b carried on the under side of fly-wheel w in 
juxtaposition to the rings c' c', and connected with wires leading to 
a magnet M, also carried on fly-wheel w, form a circuit controlled by 
relay R. Arranged concentrically around the periphery of fly-wheel w 
are a number of contact points h k, one pair for each key of the kev- 
board, or for each letter or other character on the keyboard. When 





























































MUSSO SYNCHRONOUS SYSTEM. 


171 


the coherer relay is actuated by an incoming signal, the magnet M 
allows its armature, carrying a metallic circuit-closer m, to bridge the 
contacts k k, thereby closing the circuit of a type magnet m' of a type¬ 
writer, and printing a letter. 

Assuming the fly-wheels at each station to be in synchronism, it 
is clear that at the depression of a key when the wedge v at the trans¬ 
mitting station arrives at the said key arms, a train of oscillations will 
be set up, and inasmuch as at that instant the brushes b b or the 
magnet M at the receiving station will have arrived opposite the con¬ 
tacts of the letter corresponding to the key so depressed, the desired 
letter or character will be printed. 

Devices, not shown herein, for automatically stopping and start¬ 
ing the apparatus in the absence of an attendant are employed. Also 
devices whereby any one station may lock out all stations of the same 
system excepting the one with which it is desired to hold communi¬ 
cation. See U. S. patent No. 707,012. Signor Musso has also devised 
a more sensitive relay than the ordinary filings-coherer for his system, 
consisting of fragments of magnetite and pure silver. 

The speed of transmission by synchronous telegraph systems is 
not high, and the difficulty of maintaining the necessary synchronism is 
well known. It may be noted that wireless synchronous systems do 
not have to contend with the “ tailing ” effects due to static capacity 
of wire lines, but doubtless other troubles equally difficult to overcome 
will be met with. With a wheel or disk rotating say five times per 
second, and assuming thirty letters or contacts, the duration of the 
brush or wedge on any one segment would be about of a second 
in any revolution. At a rate of one revolution per second the dura¬ 
tion on a segment would be second. It is perhaps doubtful that 
a filings-coherer and its relays could act efficiently in this time. 
Hence the speed of rotation would have to be reduced, probably to a 
rate of one revolution in three seconds, more or less, which would 
entail a slow rate of transmission, perhaps seven or eight words per 
minute. The writer has no knowledge that any wireless printing tele¬ 
graph system or synchronous wireless telegraph system is as yet in 
actual operation. 



CHAPTER XIII. 


SIGNALING BY ULTRA-VIOLET RAYS—WIRELESS TELEPHONY- 
SPEAKING LIGHT, SPEAKING ARC, ETC.—ZICKLER, BELL, 
HAYES, RUHMER, SIMON, COLLINS, ARMORL SYSTEMS. 

ZICKLER SYSTEM OF WIRELESS TELEGRAPHY BY ULTRA-VIOLET 

RAYS. 

Taking advantage of Hertz’s discovery that when ultra-violet 
rays fall upon the sparking-balls of an induction coil the sparking is 
facilitated—in other words, that an E. M. F. which ordinarily will 
not be sufficiently powerful to jump across a given gap, but will do 
so when ultra-violet rays are thrown upon the electrodes, Professor 
Karl Zickler has devised a system of telegraphing without wires by 
means of such rays, the apparatus for which is shown in Figs. 99, 99c. 

The transmitter is shown in Fig. 99. c is a case containing a 
powerful arc lamp c, using about 54 volts and 25 amperes with an 
arc of about .39 inch, the rays from which pass out normally at 
the opening w, at which is placed a shutter composed of one or more 
glass plates, glass being used for the reason that it allows the ordi¬ 
nary light rays to pass, but is opaque to the shorter ultra-violet rays. 
The shutter may be operated pneumatically, like photographic appa¬ 
ratus. The case c is adjustable in a horizontal or vertical plane, so 
that the rays issuing from the opening in the box may readily be 
directed toward the receiving station. To direct the rays a concave 
mirror or a double convex lens is employed at the transmitter, or a 
combination of both may be used, as shown in Fig. 99, at l and q 
respectively. 

The receiver is outlined in Fig. 99c. It comprises a tubular 
^rlass case G, in which are two electrodes cl s, facing each other and 
supported in the positions shown by the glass case, into which they 
are melted. The electrode s is a sphere, a few tenths of an inch in 


ZICKLER WIRELESS SYSTEM. 


173 


diameter; d is a small metal disk. The case is hermetically closed 
by a quartz plate q\ which is transparent to ultra-violet rays. A 
metal tube t, having a conical opening t\ is placed over the glass ease 
as indicated. At the left end of t' there is another quartz lens V. 
li is a screw by which the tube t may be so adjusted that the light- 
rays from the transmitter are thrown in the shape of a small oval 
spot of light upon the disk, which is placed at an angle suitable to 
reflect the received rays on to sphere s. 

The electrical connections of the receiver are also shown in Fig. 99#. 
The terminals of the electrodes are connected to the secondary of a 



Pig. 99. 
Zickler Transmitter 



Zickler Receiver. 


small induction coil I, giving a spark of about .3 to .6 inch, adjusta¬ 
ble by the resistance r; b consists of two small storage cells providing 
a current of about 1.5 amperes; s is connected to the positive pole, 
d to the negative pole. The resistance r is adjusted to keep the 
E. M. F. just below the sparking point, normally, but sparking ensues 
when the ultra-violet rays fall upon the electrodes. A coherer, an 
ordinary relay, or a telephone may be placed in the secondary circuit 
to indicate the passage of sparks across the terminals. 

The operation is then virtually as follows: The glass shutter at 
the sending station is opened and closed, thereby permitting the ultra¬ 
violet rays to pass at intervals corresponding, for example, to the 
dots and dashes of the Morse code. These ultra-violet rays reaching 
the disk d bring about the sparking in the manner aforesaid, and at 
intervals corresponding to the opening and closing of the glass shut¬ 
ter at the transmitting station. 

In other experiments in connection with this system Zickler availed 
of another of the discoveries of Hertz, namely, that the length of 
spark when illuminated and not illuminated by the ultra-violet rays 
increased up to a certain point as the air pressure in the spark-gap is 
diminished, and accordingly rarefied the air in the glass tube. 

The distance to which signals have thus far been transmitted by 




































174 


WIRELESS TELEGRAPHY. 


ultra-violet waves has been quite limited, namely, six or seven hundred 
yards; hut Professor Zickler expects to increase this distance con¬ 
siderably. It is, however, pointed out by other experimenters that 
owing to the rapidity with which these ultra-violet rays are absorbed in 
a humid atmosphere it is not likely that the distance reached by this 
method will ever exceed one mile. 



bell’s photophone or speaking light. 

Systems or apparatus by which liglit-waves or the arc lamp are 
caused to reproduce articulate speech have been termed the “ speak¬ 
ing light” and “speaking arc” respectively. Examples of each 
will be given. 

The photophone is a device due to Alexander Graham Bell, the 
inventor of the telephone, by which speech is transmitted by light¬ 
waves. The principle is shown diagrammatically in Fig. 100. A 

beam of light is concentrated 
by means of a lens l upon a 
small concave mirror, carried 
on the exact center of a suit¬ 
able diaphragm in proximity 
to a mouthpiece p. The re¬ 
flected rays are directed upon the receiving station by a double con¬ 
vex lens V. 

In the receiving system that property of selenium by which it 
varies its electrical resistance under fluctuations of light is utilized, 
s is a selenium cell, placed in the focus of a parabolic reflector f. 
The cell s is part of a local circuit with a telephone receiver t and a 
cell of battery b. Then when sounds are uttered at the mouthpiece 
the diaphragm vibrates consonantly therewith, this causing variations 
in the reflected rays from p, these variations in turn being repeated 
at the selenium cell. Hence, corresponding variations are set up in 
the resistance of the local circuit, with the result that the sounds 
uttered at the mouthpiece are reproduced in the telephone. 

The selenium cell consists of platinum wires in the shape of a 
grid, the two sections of which do not touch, but are connected by 
selenium, the wires and selenium together forming part of the circuit 
with 1) and t; thus quick variations in the resistance of the selenium 
are easily detected in the telephone. The initial or normal resistance 
of the selenium cell is very high. One cell of which the author has 





HAYES-CRAM RADIOPHONE. 


175 


knowledge ranges from 300,000 ohms in the dark to about 75,000 
ohms in the light, a ratio of 4 to 1. Other types range from 500,000 
to 25,000 ohms, and others, like Ru Inner's cell, are still more efficient, 
and will be described. Giltay suggests cutting out the selenium cell 
by means of a switch before opening the telephone circuit, to prevent 
the extra current from short-circuiting the cell. 


THE HAYES-CRAM RADIOPHONE. 



This system, due to Messrs. Hayes and Cram, of Boston, Mass., has 
been in operation for comparatively short distances in this country since 
1900, and perhaps prior thereto. The inventors have shown a number 
of variations of this device, one of which is indicated in Fig. 101. 

This figure comprises parabolic reflectors l l' facing each other; 
an arc light a in the focus of l (a is connected by wires w' w' to a 
generator d); m, a microphone transmitter in shunt with the arc 
by means of wires w iv. In the focus of the receiving reflector 1 , s is 
a substance extremely sensitive to heat. In this case a small quantity 
of carbonized fibrous material is 
used, t is a small glass bulb or tube 
in which the carbonized material is 
inclosed. Within the reflector the 
tube is sealed; outside of the tube 
it is open and is connected by 

means of a rubber tube with two ear-tips e. When the sounds are 
spoken into the transmitter M, the current flowing across the arc is 
modified by the variations in the resistance in the shunt circuit, and 
accordingly corresponding variations occur in the light of the arc. 
The reflector l reproduces these variations, although they are so 
minute as not to be visible to the eye, and they are transmitted to 
reflector l\ by which they are focused upon the carbonized material s, 
and thereupon sounds corresponding to those uttered at the dia¬ 
phragm of the transmitter M are emitted. 

In other arrangements of this system the inventors show at the 
transmitter a transformer intervening between the microphone and 
the arc-lamp circuit, and in the receiving reflector u heat sensitive 
device, such as selenium. In practice, however, the receiver has 
hitherto consisted of the material mentioned, and the maximum dis¬ 
tance at which speech has been transmitted by this device is about 
two miles. 







176 


WIRELESS TELEGRAPHY. 


THE RUHMER PHOTO-ELECTRIC PHONE. 

This is another “speaking light” system, due to Mr. E. Ruh- 
mer, which follows somewhat the line of Bell’s photophone. The 
system is outlined schematically in Fig. 102, in which A is the send¬ 
ing and b is the receiving station, m is a microphone transmitter 
with its battery b and primary coil of transformer t, the secondary 

of which is in series with 
a dynamo d which generates 
current for the arc lamp a. 
A cylindrical lens l directs 
the rays from the lamp to a 
lens V at b, where the re¬ 
ceived rays are focused upon 
a selenium cell s by the 
lens V. In the circuit of s are the telephone t and battery b. 

As in the analogous systems just described, the action of this sys¬ 
tem is due to the modifying effect of the microphone upon the cur¬ 
rent in the arc-light circuit, this producing varying degrees of illu¬ 
mination of the arc, which are detected by the sensitive selenium cell 
at the distant station, the whole resulting in the reproduction of 
speech in the telephone t. 

The distance to which Ruhmer has succeeded in transmitting 
speech by means of his “ speaking light” is about eight or ten miles. 
In his tests he employs a very sensitive microphone transmitter, using 
6 or 8 volts in its local circuit. According to Ruhmer the degree of 
illumination at the arc that is best suited to the selenium cell must 
be carefully chosen and maintained during operation. For distances 
exceeding four miles he uses an E. M. F. of G2 volts and a current 
of about 14 amperes. 

The selenium cell devised by Ruhmer for this service consists of 
a glass tube about .8 inch diameter and 1.7 inches long, around which 
are wound two fine platinum wires, over and between the interstices 
of which a coating of selenium is placed. The selenium takes the 
place of a dielectric, as it were, between the wires, separating them 
from each other, and as these wires are part of the local telephone 
circuit, the resistance of that circuit varies with that of the selenium. 
By making the selenium cell cylindrical a greater uniformity of the 





























SIMON SPEAKING ARC. 


177 


light falling upon it is secured, which is desirable. To further main¬ 
tain the uniformity of conditions surrounding the cell it is inclosed 
in an exhausted glass tube. The Ruhmer cell described has an unil¬ 
luminated resistance of about 120,000 ohms, which falls to 1500 ohms 
in a bright light. This cell also has the property of varying its resist¬ 
ance almost instantly, like a good auto-coherer—in other words, it 
has a low time constant. 

Obviously, ordinary telegraphic signals could be transmitted by 
using a sensitive relay in place of the telephone receiver, in which 
case presumably the signaling distance could be increased. The maxi¬ 
mum distance at which the light from powerful search-lights is visible 
is about thirty miles. 

THE SIMON SPEAKING ARC. 

The discovery that the electric arc could be made to reproduce 
speech was made by Dr. Simon in 1897. 

There are several ways in which this can be done. One of the 
simplest methods is outlined in Fig. 103. Here, a is the arc lamp; 
r r' are resistances; n n' are inductances; c is a condenser across the 
arc; B is a battery or dynamo; M is a microphone transmitter. When 
the voice is spoken into the transmitter the articulate sounds are repro¬ 
duced by the arc. To obtain the loudest sounds the arc should be 
long. Arcs 3.9 inches in length have been used advantageously. 




Fig. 103. Simon Speaking Arc. Fig. 104. 

In Fig. 104 another somewhat similar arrangement is shown, by 
which the variations of current set up by the voice in the primary 
circuit of transformer T are thrown on the field-magnet circuit f f 
of a dynamo machine d, with the result that all the arc lamps on the 
circuit reproduce the words spoken into the transmitter m. It has 
been suggested that by an arrangement of this kind a speaker could 
address an audience of any size by a suitable disposition of the lamps. 















178 


WIRELESS TELEGRAPHY. 


Simon has also experimented with a variation of Bell’s speaking- 
light, using as a receiver a selenium cell s, Fig. 105, in series with 
which is an inductance n and a battery b, and in shunt with the cell s 

a condenser c and telephone receiver t. 
For the transmitter he uses an arc light 
in which the positive carbon is .195 inch 
and the negative carbon .117 inch in diam¬ 
eter, supplied by a current of 3 to 5 am¬ 
peres. The arc for best results should be 
very small. By this device speech has 
been clearly transmitted 1.5 miles. 

Mr. K. A. L. Snyder also has made successful experiments with 
the speaking arc, using an arrangement practically similar to that 
shown in Fig. 103. He employs a solid-back microphone transmitter 
and a lamp and impedance coil n shunted by a condenser c, the use 
of which, Snyder claims, adds materially to the successful reproduc¬ 
tion of speech. The lamp used is a Schuster hot-wire arc lamp, 
operated at 110 volts direct current. Snyder employed a positive 
carbon impregnated with foreign substances, to take advantage of the 
fact that carbons so impregnated show a more uniform drop all the 
way across the arc, unlike the ordinary carbons, between which there 
is a great fall of potential close up to the positive carbon. 

As noted by Snyder, the most generally accepted theory of the 
speaking action of the arc is that it is due to the sudden changes in 
the temperature of the arc, which cause rapid expansion and contrac¬ 
tion of the heated air. The carbon vapor of the arc, being in a high 
state of molecular vibration, has a low specific heat. The tem¬ 
perature of the arc varies as the square of the current, and also varies 
almost concurrently with the current. Therefore, when the current 
is varied the temperature of the arc is rapidly and largely increased 
or decreased therewith, and the volume of vapor, varying as it does 
with the temperature, sets up sound-waves in the air surrounding the 
arc. (See Transactions A. I. E. E., March, 1903.) 

THE COLLINS WIRELESS TELEPHONE. 

Mr. A. F. Collins has consistently advocated the cause of wireless 
telephony for some years, and during that time has made numerous ex¬ 
periments to demonstrate its practicability, at least for short distances. 

The details of his experiments, however, have not been given out. 


Wo 


1 


- 1 


Fig. 105. 

Simon Speaking Light. 








WIRELESS FOG-SIGNALS. 


179 


pending the issuance of letters patent. In general, the Collins appa¬ 
ratus consists of an oscillator and a coherer with an electric-bell 
attachment for calling purposes, and a telephonic transmitter and 
receiver of special construction for the transmission and reception of 
articulate speech. Mr. Collins in some experiments has used the 
earth as the medium in which the electric waves set up by the voice 
are propagated.. In this case the ground connections are quite close 
together, perhaps a foot or two apart. The distance covered thus 
far is about one mile. In other experiments in New York harbor 
masts have been placed on ferryboats with wires terminating in the 
water. Electric oscillations of low frequency are set up and upon 
these the vibrations of the voice are superposed by a microphone 
transmitter, thus varying the electric waves in a manner similar to 
that in which the speaking arc is varied. Speech has been carried 
on in this way over a distance of several hundred feet between ferry¬ 
boats. The chief use of wireless telephony for such short distances 
would be in times of fog. 


WIRELESS TELEGRAPH FOG-SIGNALS. 

Mr. C. M. K el way, of London, has devised and described a com¬ 
bination of wireless telegraphy with fog-whistles for the purpose of 
indicating not only the direction from which the fog-signals are 
coming, but also the distance of the fog-whistle station. The device 
is based on the velocity of sound, about 1100 feet per second, and 
the fact that the speed of wireless signals is practically instantaneous. 
Simultaneously with the blowing of the fog-whistle at a shore station 
a wireless signal is sent. By noting the time between the wireless 
signal and the sound of the whistle the distance is easily calculated. 

To determine the direction of the fog-whistle station, since it is 
almost impossible to tell the direction from which sound emanates in 
a fog, Mr. Kelway’s plan requires the following operation: Assuming 
the first signal to have shown the vessel to be ten miles from the 
fog-whistle in some direction, the vessel would then sail say three 
miles in some direction and get another signal. Assume that the 
distance of the vessel is then seven miles from the fog-whistle. 1 his 
gives a triangle with sides of nine and seven miles and a base of thiee 
miles, which, by a simple mathematical calculation, shows the fog- 
whistle to be directly ahead. To avoid the trouble of constiucting 



ISO 


WIRELESS TELEGRAPHY. 


triangles and making calculations, the inventor has designed a tele¬ 
meter, which is “a combination of three two-foot rules divided into 
inches representing miles, and these inches subdivided into tenths 
representing cable-lengths,” and by means of which, with but little 
trouble, the direction and distance of the signal station are indicated. 

Another inventor has devised a scheme by means of which vessels 
equipped with wireless telegraph apparatus may be apprised of their 
distance from a shore station during a fog. The shore station is 
equipped with vertical masts of say three different heights. Signals 
are sent at stated intervals from the shore from each of the masts 
consecutively. Obviously, the signals sent from the higher masts 
will affect a coherer at the greater distance. Hence, if a ship gets 
first a certain signal, say twice repeated, and then after sailing for 
some time gets a signal thrice repeated, it is evident the vessel is 
approaching the station, or vice versa. 


THE ARMORL WIRELESS TELEGRAPH SYSTEM. 

This system derives its name from the first syllable of the names 
of its inventors, Messrs. Armstrong and Orling. The device should 

hardly be included in the category 
of wireless telegraph systems proper, 
but may be described as a type of con¬ 
duction systems. 

The sending and receiving arrange¬ 
ments are indicated in Fig. 106. The 
receiver is a relay based on the capil¬ 
lary action of an electric current on 
a liquid contained in a tube, j is a 
vessel filled with mercury, into which 
one tube of a siphon b enters ; the 
other end of the siphon enters a cell h 
containing acidulated water x. The 
siphon is open at both ends. A deli¬ 
cate metal balance or beam b is piv¬ 
oted on an agate bearing n. The 
right-hand end of b descends, as shown, 
below the end of the siphon in x and almost touches it. The other 
end of b carries a contact l which controls a local circuit consist- 



Fig. 106. 

Armorl Wireless System. 
















































ARMORL WIRELESS SYSTEM. 


181 


mg of the wire n\ «. small battery V , and the magnet of a Morse 
register i, with its paper-reel R. The siphon is also filled with mer- 
cury. ihe positive pole of the external circuit enters the siphon 
thiough a stoppei at c, aud the negative pole at the cell h , as indi¬ 
cated. When a current enters at the positive pole capillary action 
causes a small drop of mercury to pass from the lower end of the tube 
upon the end of the balance b. This raises the left end of that beam, 
closing the local circuit and opening the magnet. When the right 
end of b is thus depressed the mercury drops to the floor of the cell. 
This apparatus is said to be more sensitive than the telephone as a 
receiver. 

In the transmission and reception of messages the iron spikes g 
are inserted in the earth to the depth of two feet and about fifteen 
feet apart. For transmitting, a Morse key k and a battery of about 
eight volts is used, and a telephone receiver, not shown in figure, is held 
by the operator. In receiving, the battery and telephone are cut out. 
It is stated that signals have been transmitted to a distance of fifteen 
miles through the earth with this apparatus, but authentic data on the 

The same inventors have devised a wireless telephone system in 
which the transmitting apparatus in Fig. 106 is replaced by a tele¬ 
phone transmitter in shunt with an inductance coil. The trans¬ 
mitter is also in shunt with the local ground portion of the circuit 
between the stakes g. The current is supplied by a battery between 
one terminal of the inductance coil or transmitter and the earth. 
The function of the inductance coil is to augment the current varia¬ 
tions. For example, according to the inventors, when the resistance 
of the transmitter is suddenly increased the current in the earth por¬ 
tion of the local circuit is thereby increased, which increase is aug¬ 
mented by the discharge or “ kick 99 from the inductance coil which 
occurs at the same time. At the distant station the signals are 
received by a telephone receiver whose terminals are grounded a short 
distance apart. Experiment seems to show that the current does not 
follow a direct path from one stake g to the other, but appears to 
spread out over a large area like ripples over the surface of water, the 
ripples being about 180° apart in phase. Hence, if a receiver be so 
grounded that there is a difference in the potential at its respective 
terminals, sounds will be heard corresponding to the variations of cur¬ 
rent at the transmitter. 


CHAPTER XIV. 


DETECTORS—INTERRUPTERS—TRANSFORMERS—SPARK-GAP— 
CONDENSERS—ANTENNiE—TIGHT AND LOOSE COUP¬ 
LING-TUNING COILS—VARIOMETERS. 

ELECTRIC WAVE DETECTORS. 

The term “coherer” was first used by Sir 0. Lodge in connection 
with a phenomenon discovered by him, namely, that when two metal 
electrodes are in slight contact, electric oscillations in the circuit 
cause them to cohere; a slight tapping sufficing to decohere them. 
This term was subsequently applied to the filings-coherer, and more or 
less generally to all other types of electric wave detector. Inasmuch, 
however, as several of the newer detectors are in nowise coherers in 
the sense mentioned, other terms, such as the Marconi magnetic 
detector, the De Forest electrolytic responder, and the Fessenden 
barretter, have come into use, together with the terms auto-coherer, 
anti-coherer, etc., to indicate more definitely the particular types of 
detectors intended. As a generic term for all types of electric wave 
detectors, Professor J. A. Fleming has suggested the word “kuma- 
scope,” from two Greek words signifying “wave spy.” Following 
this suggestion, other writers have proposed the term “kulnagram’ , 
for a wireless or wave message. The present writer has more than once 
proposed the terms “ondescope,” “ on degraph, and “ondegram,” 
from the French “onde” (wave), as being descriptive and euphonic, 
even if not altogether acceptable to philologists. 

The cause of the change in the electrical resistance of the parti¬ 
cles of a filings-coherer when acted upon by electric oscillations is not 
absolutely known. Arons and others have investigated their action 
under the microscope, and found that when the filings are brought 
into imperfect contact (having at such a time high resistance) almost 
perfect contact is made simultaneously with the occurrence of electric 


FI LINGS-COHERERS. 


183 


oscillations. Arons noticed that the filings were violently agitated 
and saw sparks playing among them. It was also found that the 
contacts were destroyed after continued exposure to the waves, and 
that the coherers became fatigued after a time, which latter result 
has been observed by Marconi and others. It has been suggested 
that the effect mentioned is a magnetic one, but this view is not held 
to be tenable, because non-magnetic substances, such as powdered 
plaster of Paris, are also attracted under the influence of electric oscil¬ 
lations. The generally accepted explanation is that the filings are 
electrostatically attracted to one another with sufficient pressure in 
the case of metal filings to bring about a fall in their resistance. 
Lodge considers it a singular variety of electric welding. On this 
assumption, the filings should be few in number, that the E. M. F. 
may not be too much subdivided, light in weight, and not easily 
oxidizable. Aluminum has been proposed for its lightness, but is 
unsuitable owing to the readiness with which it takes on a coating of 
oxide, which introduces a high resistance that renders the metal 
too insensitive for the purpose. Tests have shown that after the 
filings have been acted upon by a heavy discharge and thus cohered, 
if then subjected to a lighter discharge the filings lose some of their 
conducting qualities. Lodge has shown that the resistance of the 
filings appears to vary directly with the intensity of the electric waves, 
and has availed of this fact to decohere the filings, namely, by send¬ 
ing weaker waves from an available source momentarily through the 
coherer. Still another theory to explain the said change of resistance 
in the coherer is that the air that is known to exist between par¬ 
ticles, even when in so-called light contact, is dissipated by an increase 
of surface tension over such surfaces, due to the electric oscillations. 
It has been found that a certain minimum resistance exists during 
the time that the coherer is acted upon by the oscillations. If the 
normal stable equilibrium corresponds to a value nearly equal to this 
minimum, the condition is that of the ordinary coherer. If, con¬ 
trariwise, the equilibrium is unstable, the coherer can decohere spon¬ 
taneously, or is auto-decohering. An explanation of this by M. Hur- 
muzeseu is that the action of the electric oscillations produces sparks 
between the metallic filings, which cause them to weld, occasioning 
thereby real coherence, which requires tapping to decohere. Or the 
oscillations produce brush discharges which oxidize the particles, and 
thereby increases the resistance of the metallic chain, producing anti- 


184 


WIRELESS TELEGRAPHY. 


coherence. If the metal is not in an oxidizing atmosphere and the 
cohesion is not determined by welding, the brush discharge ceases 
with the oscillations, producing auto-coherence. 

M. 0. De Bast considers a filings or powder coherer as a group of 
very small condensers arranged in series parallel (see De Forest Ley¬ 
den jar arrangement), each pair of particles being separated by a thin 
coating of oxide, thus forming opposite plates of a simple condenser 
of very small capacity. If the difference of potential of the vertical 
wire be sufficient to cause a spark in the coherer with which it is in 
series, the spark passes from particle to particle, tearing off at each 
gap a small part of the oxide coating and making a metallic contact 
which allows the battery current to flow, a slight tap separating 
tire particles. 

Experiments by Mr. Carl Kinsley have shown that the filings 
cohere under an E. M. F. of from 2.5 to 5 volts, depending on the 
sensitiveness of the coherer, there being apparently a critical E. M. F. 
for each coherer. This is tantamount to saying that each coherer 
possesses a “ figure of merit,” as the phrase has long been used in teleg¬ 
raphy, namely, the reciprocal of the least amount of E. M. F. or 
current to which it will respond operatively, and this applies to all 
types of wave detectors. (See Fessenden tests, end of this section.) 

E. Dorn examined various metals under different conditions as 
to their suitability for coherers, and noticed that the noble metals, 
platinum, gold, and silver, gave practically no change of resistance. 
Copper filings at first gave no change of resistance, but after some 
hours a slight change was noticed, and in three weeks the initial 
resistance was 300,000 ohms instead of one ohm, as in the first 
instance. Then after exposure to electric oscillations the resistance 
fell to 10 ohms. After tapping, resistance rose to 187,000 ohms. A. 
tuning-fork nearby reduced the resistance to 10,000 ohms. Some 
early experiments by E. Aschkinass demonstrated that powdered 
peroxide of lead acts as a coherer. Ko chemical reaction appears to 
take place even after prolonged exposure to the oscillations. He 
observed, somewhat contrary to Dorn, that some of the noble metals, 
like silver, gold, and platinum, acted as a coherer after severe shaking; 
further, that a gentle heat tends to restore coherefs to their original 
resistance, and that a hot coherer is “ self-righting,” another term 
for auto-decohering. The chief difficulty now found with coherers 
of silver, gold, and platinum filings is their great sensitiveness; and,- 


TURPAIN RESONATOR—CARBON DETECTORS. 


185 


as has been noted, Marconi uses a small percentage of silver in his 
coherer to increase its sensitiveness. 

M. Turpain, in his work “ Ondes Electrique,” points out that if 
in a Hertz resonator r, Fig. 107, an opening s' of say 1.2 inches, inde¬ 
pendent of that at the micrometer-screw s, be made, and if a tele¬ 
phone t Avith battery b be placed in the 
opening s', the resonator will work as 
efficiently as when complete. At the mo¬ 
ment the sparks virtually close the cir¬ 
cuit by reducing the resistance of the 

spark-gap s the effect is noticeable in the m 0 

1 ° r , Turpain Resonator. 

telephone. It is not the oscillations that 

affect the telephone, but the closing of the circuit at the spark-gap 
that varies the E. M. F. of the battery and thus produces the sounds 
in the phone; this affording not only an easy means of studying the 
waves, but also providing a more delicate and satisfactory method, the 
ear being a much better organ for detecting the variation in the sound 
Lhan the eye is of variations in light. The oscillations emitted by the 
ex* iter have a very short period, being of the order of billions per 
second, and the receiver, vibrating in unison with the exciter, has a 
similar period. The effect at the micrometer is not produced by a 
billion of sparks per second, but by billions of variations of potential 
per second. The eye as regards the sparks cannot take account of 
their extreme rapidity and sees them as one group, while in fact each 
group is made up of ten millions of oscillations. In short, M. Tur¬ 
pain adds, the telephone is in this respect about ten times more 
sensitive than the eye. 

Mr. F. J. Jervis-Smith states that very fine carbon powder, made 
from electric-lamp carbon, and placed in a small glass tube with suita¬ 
ble pointed electrodes, and in circuit with a galvanometer of 50 ohms, 
a resistance of 8000 ohms, and one dry cell of 1.4 volts, makes a 
detector very sensitive to electrical disturbances. 

The utility of carbon powder, as well as many other types of auto¬ 
coherers, is somewhat limited by the fact that the variation in the 
resistance before and after cohering is very small, thus requiring a 
very sensitive instrument to detect the variations. Mr. S. A. Varley 
was probably the first to show the effect of high tension and alter¬ 
nating currents in breaking down the resistance of carbon particles, 
and before 1870 availed of this property of carbon for a form of 








18G 


WIRELESS TELEGRAPHY. 


lightning arrester. He also showed that the resistance of carbon 
decreased with an increase of temperature. 

Branly showed that two steel needles slightly rusted and laid 
across each other will act as a coherer. Fenyi notes that a very 
strong current can be used with a number of steel needle-coherers in 
series. With six such coherers in series they may be connected up 
with a primary cell of 1.5 volts. If several cells are to be used, three 
or four coherers must be added for every additional volt. In this way 
currents of one tenth of an ampere may be employed. In one experi¬ 
ment Fenyi had six needle-coherers in circuit with an electric bell 
and a Leclanclie cell. A small spark excites the coherer and the bell 
rings. The vibration of the bell decoheres the coherer. This coherer 
may be used to announce distant thunder-storms if put to earth on 
one side and connected with an insulated wire 100 to 1000 feet long— 
the greater length of wire giving the best results. 

Mr. R. H. Bell, San Francisco, finds that a simple mixture of silver 
and carbon filings with a very small amount of iron filings made an 
excellent powder for a coherer. He describes another coherer con¬ 
sisting of a microphone in which one set of carbon pencils is replaced 
by a narrow strip of tin-foil. The instrument is inclined until the 
foil rests lightly against the lower carbon. The foil is attached to 
the upper pencil, and the pressure of the foil is regulated by a delicate 
spring. The lower carbon is filed down to a rather sharp edge. A 
relay is connected in the usual way. Five Leclanche cells are used. 
An advantage claimed is that by varying the pressure of the foil on 
the carbon clear and decisive signals can be obtained. 

Alex. Poppoff has described, practically as follows, an auto-coherer 
consisting of a glass tube with electrodes composed of small blades of 
platina lapping over each other in the tube. The filings are hard 
steel grains with sharply defined edges, and a granular fracture, pre¬ 
pared so as to permit of varying degrees of oxidation of surface. The 
grains are made from ordinary steel beads, crushed into splinters and 
oxidized. The rounded and polished exteriors take but a very thin 
layer of oxide; the inner or unpolished parts take a thicker layer; 
while those surfaces that correspond to the cleavage are almost exempt 
from oxide. 

Mr. James Foster King has patented a coherer and receiving sys¬ 
tem which consists of an exhausted glass tube in which are two flat 
silver electrodes insulated from each other longitudinally. The filings, 


KING, MINCHIN, RIGHI COHERERS. 187 

which rest on these plates, have a magnetic core of iron, over which 
is a thin coating of platinum that resists sparks and is also a good 
conductor, hence allowing more current to flow than would otherwise 
do so. The top of the glass tube is attached to a magnet which in 
turn is connected to the core of an induction coil. The relay is in 
the secondary wire of this coil, the primary of which is in series with 
the coherer, a small battery, an inductance coil, and part of the aerial 
wire. The other terminal of the coherer is to earth. When oscilla¬ 
tions occur, the particles cohere and a current flows through the pri¬ 
mary wire. This induces a current in the secondary, which operates 
the relay and at the same time magnetizes the pole-piece which 
attracts the magnetic particles, decohering them. 

Professor G. M. Minchin has devised an auto-coherer which he 
has found very sensitive, namely, a glass tube in which is placed a 
small carbon pencil about .5 inch in length, upheld by two aluminum 
stirrups, curved lower ends of which form a cradle in which the pen¬ 
cil loosely rests. The vertical wire, at the top of which is a large 
plate, is attached to one of the aluminum wires; the other is grounded 
through a coil of high inductance but low resistance. A small bat¬ 
tery and a telephone receiver shunt the coherer in the usual way. 
A modification of this coherer comprises a glass tube on the bottom 
of which is placed some mercury. The carbon pencil is upheld by 
the aluminum stirrups as before. A platinum electrode is connected 
to both of the stirrups in parallel. The other electrode rests in the 
mercury A platinum wire connects the pencil with the meicui\. 
Before the tube is sealed the mercury is boiled, thus leaving a mercury 
vapor in the tube. This detector decoheres promptly with a telephone 
receiver, but as the aluminum stirrups are in parallel both must act 
before a relay will operate without tapping. In the ariangement fiist 
described a relay should operate when but one of the contacts acts. 

A detector due to M. Righi consists of a tube in which are a 
rarefied gas and two electrodes very close togethei (.039 inch), in cii- 
cuit with a batter) 7 the strength of which is just a little below that 
necessary to pass current. When electric waves are set up in its 
vicinity the tube is illuminated, and the illumination ceases with the 
waves or oscillations. A galvanometer, which will return to zeio 
when the waves cease, may be placed in the circuit. 

M. Tissot has designed a coherer the tube of which is carried by 
the armature-lever of a magnet. When the coherer is operated the 


188 


WIRELESS TELEGRAPHY. 


armature-lever of a polarized relay closes the circuit of said magnet 
and the coherer tube is attracted, imparting a slight shock to the 
coherer, decohering it. He also found that the sensitiveness of a 
nickel-iron filings-coherer is increased by placing the tube parallel 
with the lines of the magnetic field, which, it has been suggested, is 
due to increased cohesion of the filings. Mr. C. G. Brown describes 
a detector which is decohered by magnetism. He uses iron or nickel 
filings in a tube having iron electrodes. A permanent magnet is 
caused to revolve before the electrodes, or they may be surrounded by 
a coil carrying alternating currents. In the presence of oscillations 
the filings cohere in the usual way, but when the waves cease the 
filings decohere, the external magnetism evidently drawing the par¬ 
ticles apart. Mr. Brown also showed that the resistance of a vibrating 
contact is decreased by electric oscillations. Another writer has noted 
the analogy between the microphone as an imperfect contact apparatus 
which detects minute sound-waves, and the coherer as an imperfect 
contact device for detecting the minute electric waves. With regard 
to the detector variously known as the Castelli, Solari, and Ivoyal 
Italian navy coherer (page 09), it may be stated that this detector was 
first described by Professor Tommasina in a note to a Geneva society, 
which was published in “ L’Elettrieita,” Milan, July 7, 1900, which 
note mentions, among other coherers, one consisting of a drop of 
mercury between two carbon electrodes. Mr. J. Gavey finds that a 
.sharpened pencil, adjusted and resting lightly on a steel spring, with 
a little spot of oil at the point of contact, acts very well as a detector. 
With this receiver he has picked up signals of all sorts of wave¬ 
lengths from stations in England and France. 

The modification of the Marconi magnetic detector referred to on 


page 71 is outlined in Fig. 108. p p are the pulleys, about an inch 

in diameter, operated by 
clockwork; cc represents 
the iron band which passes 
through a small glass tube 
upon v 7 hich coils w iv' are 
wound. The iron band is 
about eighteen inches in 
length, and is made up of a number of small iron wires, each about 
.005 inch in diameter, held together and covered by silk or cotton 
thread or braid, the outside diameter being nearly one eighth of an inch. 



Fig. 108. Marconi Magnetic Detector. 












MAGNETIC DETECTORS. 


189 


The band is magnetized by two ordinary horseshoe magnets (not shown 
in the figure), the ends of which are loosely laid, with their similar 
poles together, on the coils, and are adjusted as to their position on the 
coils until best results are obtained. The legs of the magnets are 
about four inches in length. While this detector is said to be very 
sensitive, the sounds which it produces in the telephone are very 
minute and require a keen ear to detect them. The writer’s expe¬ 
rience with several different forms of sensitive detectors in which the 
telephone is used would indicate that a sound-proof booth would be 
a valuable adjunct to the receiving system, as even the humming of 
an oil engine in an adjoining room has a disturbing effect upon the 
operator receiving the signals. In practice the filings-coherer and 
magnetic detector are interchangeable by means of a switch which con¬ 
nects one or other to the antenna as desired. In Marconi’s latest 
form of filings-coherer the inner ends of the leading-in plugs are 
wedge-shaped, for a similar purpose to that described in connection 
with the Slaby-Arco coherer (page 90). The Marconi tapper is a 
small brass ball, less than .25 inch in diameter, carried on the end of 
an armature-lever; its motion is quite limited, and it strikes the tube 
lightly but rapidly. 

Magnetic detectors in general are based upon the discovery of 
Professor E. Rutherford that when a very small magnetized iron wire 
is placed in the center of a coil of wire, the ends of which are con¬ 
nected to antennae or wings, electric oscillations in the coil have the 
effect of hastening the demagnetizing of the iron, as mentioned on 
page 71, which effect Rutherford observed by means of a magnetom¬ 
eter, a device similar to the mirror of 
a Thomson reflecting galvanometer, the 
movement of which indicates a greater 
or lesser degree of magnetism in its 
vicinity. 

Another magnetic detector employ¬ 
ing this principle, due to Mr. II. Shoe¬ 
maker, is shown in Fig. 109. In this 
a permanent magnet, with poles N s, is 
suspended by an arm or axle a, which is 
rigidly attached to the pulley p'. The latter is rotated by clockwork. 
A number of small iron wires c (No. 2G gauge), forming a core about 
.4 inch in diameter and 3 inches long, is surrounded by primary 


— 

(-- 

A 

M/IPI 

o _^_ _ . 

3 



Fig. 109. Shoemaker Mag¬ 
netic Detector. 



















190 


WIRELESS TELEGRAPHY. 


and secondary coils p s. The primary consists of one layer of 
No. 26 B. & S. wire; the secondary, of seven layers of No. 36 B. & S. 
wire. The terminals of the primary are connected with the aerial 
wire A and earth; the secondary has iirits circuit a telephone receiver t. 
The rotation of the magnet around the core c produces changes of 
magnetism in the core which normally are not apparent in the tele¬ 
phone circuit. When, however, oscillations are set up in the aerial 
wire rapid changes of magnetism are effected in the core, and these 
set up currents in the secondary that are easily detected in the tele¬ 
phone t. This detector is not very sensitive, but has been found 
quite efficient up to distances of 25 miles with 24 vertical wires 
160 feet in height. 

Dr. Lee De Forest also employs a sensitive magnetic detector, 
based on the Rutherford principle, the details of which are not yet 
ready for publication. 

Another utilization of the Rutherford discovery, due to Professor 
J. A. Fleming, is one for the purpose of determining quantitatively 
the wave-making power of different wave-radiators, the efficiency of 
different forms of spark-gaps, oscillating circuits, etc., and is described 
by the inventor as follows: A pasteboard tube .75 inch in diameter 
and 6 inches long is surrounded with 6 coils of No. 40 silk-covered 
copper wire, each containing about 6000 turns. The coils are joined 
in series and have a resistance of aboat 6000 ohms. Inside the 
tube are placed 8 small bundles of iron wire 6 inches in length, each 
bundle being composed of 8 wires of No. 26 S. W. G., previously 
well paraffined or painted with shellac. Each bundle is wound over 
uniformly with a magnetizing coil formed of No. 36 silk-covered cop¬ 
per wire in one layer; and over this, but separated from it by one or 
two layers of gutta-percha tissue, is wound a single layer of No. 26 
wire, forming a demagnetizing coil. This last coil is, in turn, cov¬ 
ered over with one or two layers of gutta-percha. The magnetizing 
coils are connected in series with one another, so that when a 
current passes through the whole of them it magnetizes all the 
bundles in the same sense. The outer or demagnetizing coils are 
joined in parallel. In addition to this coil there is a rotating com¬ 
mutator, consisting of a number of hard fiber disks, secured on a steel 
shaft driven by an electric motor at about 500 turns a minute. There 
are four of these disks, and each has let into its periphery a strip of 
brass, occupying a certain angle of the circumference. The brass 


FLEMING WAVE-INDICATOR. 


191 


sector of the first disk occupies 95 degrees of the circumference. The 
brass sectors of the second and third disks occupy 135 degrees of the 
circumference, and that of the last disk, 140 degrees. Brass brushes 
make contact with these disks, and serve to interrupt or make elec¬ 
trical circuits as they revolve. The function of the first disk is to 
make and break the circuit of the magnetizing coils placed around 
the bundles of iron wire, thus applying a magnetizing current during 
a portion of one period of rotation of the disk, leaving them mag¬ 
netized during the remaining portion. The function of the second and 
third disks is to short-circuit the terminals of the secondary coil of the 
bobbin during the time that the magnetizing current is being applied 
by the first disk. A sensitive movable-coil galvanometer is employed 
in connection with the secondary coil, one terminal of the galva¬ 
nometer being permanently connected to one terminal of the secondary 
coil, and the other terminal connected through the intermittent con¬ 
tact made by the fourth disk. This disk is set so that the time the 
secondary coil is short-circuited, and while the battery current is being 
applied to magnetize the Avires, the galvanometer circuit is opened. 
During one complete revolution the operation goes on as follows: 
First, the magnetizing current of a battery of secondary cells is applied 
to magnetize the iron bundles, and during the time that this mag¬ 
netizing current is being applied, the terminals of the fine-wire 
secondary coil are short-circuited, and the galvanometer is discon¬ 
nected. Shortly after the magnetizing current is interrupted, the 
secondary bobbin is un-short-circuited, and an instant afterward the 
galvanometer circuit is completed and remains completed during the 
remainder of one revolution. If, during the period when the gal¬ 
vanometer is connected to the secondary coil, an electrical oscillation 
is passed through the demagnetizing coils, an electromotive force is 
induced in the secondary bobbin by the demagnetization of the iron, 
and causes a deflection of the galvanometer. Since the rotation of 
the commutator is rapid, these impulses produce a continuous deflec¬ 
tion of the galvanometer which is proportional to the demagnetizing 
force being applied to the iron. The instrument can be employed as 
a telegraphic receiving instrument, or it can be used to verify the law 
according to which radiation falls off with distance. For comparing 
together the wave-making power of different radiators the oscil¬ 
lation coils must be conducted to two long connecting wires, or 
one end may be connected to the earth and the other to a ver- 


102 


WIRELESS TELEGRAPHY. 


tical aerial. Professor Fleming suggests that this instrument will 
not only be found of great value in the design of radiators and 
transmitters for Hertzian-wave wireless telegraphy, but also in the 
investigation of the transparency or opacity of various substances to 
Hertzian waves. The instrument may be made as large as desira¬ 
ble, but it is necessary that the iron wires be quite small, and that 
they be assembled in small bundles. It is also necessary to short- 
circuit the fine-wire secondary coil, as described above, during the 
time of magnetization of the core. 

Professor P. Fessenden has recently patented a liquid barretter, 
which is said to be much more sensitive than the hot-wire barretter 
mentioned in connection with the Fessenden wireless system. A 
number of such detectors are described. One such consists of a small 
cup across the inner center of which is placed a glass diaphragm. A 
small hole is formed in the center of this diaphragm, into which hole 
a capillary tube, having an inside diameter of about .003 inch, is 
cemented, after which the ends of the tube are ground off until they 
are flush with the diaphragm. The cup is filled with a liquid solu¬ 
tion, and the diaphragm forms a partition between two portions of the 
solution, these portions being thus separated except by the thin 
column of the liquid in the capillary tube, which column forms the 
barretter. A small platinum wire connected with the vertical wire 
extends into the upper portion of the solution, while a similar plati¬ 
num wire connected to earth enters the lower portion of the solution 
through the cup; or these wires may be in the secondary circuit of a 
transformer. Another form of liquid barretter consists of a minute 
fiber, such as a cotton thread, which is used as the loop of a barretter, 
the liquid being supplied to the loop by capillary action. Professor 
Fessenden has found that such liquids as carbonate of soda and nitrate 
of potash give good results, but nitric acid is preferred, as the effects 
obtained by its use are the strongest. Some of the advantages of 
liquid barretters noted by the inventor are that by reason of their 
nature they are not injured by excessive discharges; also, the specific 
resistance of liquids is muchTiigher than that of metals, in some cases as 
much as a million times greater, and, consequently, to obtain the same 
resistance a very much smaller mass, capable of being heated to a much 
larger extent, may be used; further, the amount of change of resist¬ 
ance per degree of temperature is very much greater—for example, 
the resistance of sulphuric acid when not quite concentrated changes 


LIQUID DETECTORS. 


103 


approximately twelve per cent, per degree centigrade, while the-change 
in platinum is only about one third of one per cent. With a liquid 
barretter having a resistance of 600 or 2000 ohms the increase of con¬ 
ductivity when the liquid is heated is so marked as to permit of the 
operation of a siphon recorder, though a telephone may be used 
when desired. 

It has been noticed in practice that the precautions found neces¬ 
sary to protect the coherer from extraneous waves when very sensitive 
coherers are used are not so essential with less sensitive coherers. In 
the latter case, if the disturbing circuits are shunted with non-induc¬ 
tive resistance it is sufficient. The quality of the tap imparted to 
the tube has an important bearing on the facility with which the 
coherer will resume its original resistance. Some experimenters have 
found that blows at regular intervals are preferable to a series of 
blows at irregular intervals. Coherers made from the magnetic metals, 
iron, nickel, and cobalt, have been found to give best results in practice. 

A common way of ascertaining the sensitiveness of a coherer or. 
detector is to operate a small electric bell or buzzer in its vicinity 
with one or two dry cells. For instance, in the case of the De Forest 
responder, which is freely exposed to extraneous waves, as shown in 
Fig. 86, the adjustment of the instrument may be regulated by the 
waves set up by such a bell or buzzer, the distance of the bell from 
the antenna giving a clue to the sensitiveness of the adjustment. A 
filings-coherer for operating at a distance of about twelve miles should 
be sensitive to such a bell at a distance of at least six feet. A very 
sensitive coherer will be affected by the oscillations thus set up at a 
distance of forty or fifty feet and with doors and walls intervening. 
The opening of a switch of an electric light circuit or a near-by key 
of a telegraph circuit will also affect such a coherer or detector. 

A crude but simple method employed by the writer for showing the 
action of electric waves upon filings is as follows: Strew some nickel 
filings on the center of a piece of drawing-paper or on a visiting-card. 
Filings obtained by filing a five-cent nickel jhece with a rough file 
are suitable. Insert two common pins through the card so that their 
points come nearly together in the filings. Attach fine wire to the 
heads of the pins and lead them to the relay or galvanometer circuit. 
The writer has used for this purpose a 150-ohm Hughes relay. A 
common electric call-bell is placed in circuit with the armature- 
points of the relay. With a battery of five or six dry cells in 


104 


WIRELESS TELEGRAPHY. 


the call-bell circuit it is found that the sparks at the local contact 
points set up sufficiently energetic waves to affect the coherer. The 
sparks are first established by closing the armature of the relay with 
the finger. The filings then cohere and remain so until the card¬ 
board is .tapped with the finger. A common static electric gas- 

lighter may also be used to set up the oscillations. 

Mr W. J. Clarke, of New York, who was perhaps the first 

experimenter with wireless telegraphy in this country, has designed 
several variations of the oscillator and coherer circuits and apparatus, 
some of which as used for simple experiments are shown in 1‘ ig s - 1 J- 
and 111. In Fig. 110, i is the two-inch spark induction coil of the 



oscillator, which latter is placed at any proper distance from the 
receiver; bb are the spark-balls, about one inch in diameter, con¬ 
nected to a short wire A and ground, and to the secondary coil s; p is 
the primary coil. The coil has a core (not shown) of small soft-iron 
wires, an end of which is opposite the hammer armature h, which, in 
operation, vibrates to and fro against contact-point c'. The hammer 
interrupter h is shunted by condenser c placed in the base of instru¬ 
ment. This condenser is made of about eighty sheets of tin-foil, 
eight inches long by four inches wide, each sheet separated by thin 
paraffin paper. The resistance of the primary wire is about 2 ohms, 
No. 17 wire, that of the secondary about 3200 ohms, No. 35 wire, k is 
a Morse key in the primary circuit. The battery b, which may con¬ 
sist of five or six dry cells, is connected to posts x x. Fig. Ill repre¬ 
sents apparatus and circuits by means of which Mr. Clarke experi¬ 
mentally demonstrated the blowing up of miniature ships, etc., in a 
tank of water. This arrangement of a separate coherer may be used 














































CLARKE EXPERIMENTS. 


195 


for any purpose in which the closing of a circuit at a distance with¬ 
out wires is desired, as, for instance, in firing cannon, exploding 
mines, etc. For this work the coherer should not be too sensitive, as 
stray waves might prematurely close the circuit. In the figure, k is a 
coherer without the tapper; b V are batteries; r is a Morse relay of 
about 100 ohms resistance; d is a detonator placed under a boat or 
in the mine. 

The filings are indicated by the dark vertical line at the center of 
the tube. Mr. Clarke uses 40 to GO small nickel filings. Small brass 
rods attached to the milled heads n n' are inserted in the tube. The 
position of the rods in the tube is adjusted by screws s s', spiral 
springs r r tending to withdraw the rods, which are held in any posi¬ 
tion by set-screws h W. Vertical wires a a 10 to 20 feet high are 
attached to the outer screw posts; the wires of the relay and coherer 
circuit to the inner posts as indicated. In this use of the coherer 
the filings are decohered by tapping with the fingers or a pencil. 
The mode of adjusting this coherer is as follows: The rods in the 
tube are separated until the filings do not close the circuit. The 
coherer is then short-circuited by a piece of wire or a strap key k. 
{As stated elsewhere, a very sensitive coherer may be short-circuited 
by touching the moistened fingers to its terminals.) This closes the 
relay circuit. The armature of the relay R is then adjusted by open¬ 
ing and closing the switch w, the play of the armature-lever between 
its contact-points being very small and the pull of the retractile 
spring m very weak, the relay being operated with one dry cell b. 
The strap key is then left open and the near-by oscillator i is operated. 
The transmitter is then operated and the coherer rods or electrodes 
are then pushed in until the filings cohere sufficiently under the 
influence of the electric waves to close the relay. . The transmitter is 
opened and the coherer is decohered by tapping. Normally the cir¬ 
cuit is open at the coherer. It is essential to place a switch w’ in the 
detonator circuit to hold the circuit open until the preliminary 
arrangements are made. 

The detonator usually consists of a mixture of gunpowder with 
about 100 grains of fulminate of mercury placed in a one-ounce round 
vial. As this preparation is somewhat dangerous to transport, a two- 
ounce vial filled with about 1.25 ounces of F. F. G. rifle powder may 
be substituted. A “powder head ” is placed in the vial, and the wires 
are led out at one side of the cork, the bottle then being sealed with 


196 


WIRELESS TELEGRAPHY. 


“ electrical” cement. According to Mr. Clarke this cement is made 
as follows: 5 lbs. resin, 2 lbs. beeswax, ^ lb. red ochre, 2 oz. plaster 
of Paris. Melt with gentle heat and rigidly exclude flames. r I he 
bottle is hung so that the cork is three or four inches below the bot¬ 
tom of the boat. In this experiment care should be exercised to see 
that the bottle hangs straight down in the water, as otherwise the 
glass of the vial may be driven out of the water by the explosion. 
If, however, a small quantity of the fulminate of mercury is used, the 
glass will be pulverized and thus rendered harmless. Otherwise the 
powder alone is sufficient. 

When a sounder or register is placed in the circuit of b in place 
of the detonator, and when a tapper is used, the latter is adjusted 
until the best results are obtained, which is indicated by the nature 
of the signals received. It may be noted that from the broken-up 
character of the signals received by a filings-coherer, careful adjust¬ 
ment of the register is necessary in order to obtain readable signals. 
The difficulty is increased, according to the writer’s experience, when 
the attempt is made to receive the signals by sound on the ordinary 
Morse sounder. Signals may be read from the sounds of the tapper, 
which vibrates with the armature of the relay. 

A number of inventors, notably Mr. Nikola Tesla, have suggested 
the use of coherers and wireless telegraphy for directing the move¬ 
ments of submarine or torpedo boats, and to ignite explosives on such 
boats. This would be effected by means of motors set to perform 
different operations upon such a vessel, each motor being controlled 
from a given point by a series of wireless telegraph receivers attuned 
to different rates of electric waves. One such motor might start the 
engine, one or more would operate the steering gear, etc. 

Professor Fessenden gives the following valuable data as to the 
relative and absolute efficiencies of different wave detectors. Elec¬ 
trical energy required to operate the Marconi filings-coherer, 4 ergs 
per dot (one erg — one ten-millionth watt). The gold-bismuth de¬ 
tector (gold 95 per cent., bismuth 5 per cent., alloy), 1 erg per dot. 
Solari receiver and various types of carbon-steel, steel-aluminum, and 
steel-mercury detectors, 0.22 erg per dot. Magnetic hysteresis detector, 
0.1 erg per dot. Hot-wire barretter, 0.080 erg per dot. Liquid 
barretter, 0.007 erg per dot. In the tests which gave these results 
the detectors were adjusted to their maximum operative sensitiveness, 
and the telephone indicator receivers were adjusted to a point at 


SENSITIVENESS OF DETECTORS. 


107 


which they were just stable when not acted upon, and to give a 
change of current of ten one-millionth amperes in the telephone. 

Considered from a practical standpoint, there are, it may be said, 
two general types of electric-wave detectors, namely, the recording 
and non-recording. The first includes those detectors in which the 
variation of resistance or current produced by the oscillations is suffi¬ 
cient to operate a relay of some kind; the second includes those in 
which the variation of resistance or current is not sufficient to operate 
a relay, but yet suffices to produce signals in a telephone receiver, the 
supersensitiveness of which instrument is well known. (Calculations 
have shown that this instrument is responsive to an amount of elec¬ 
trical energy represented by the one-millionth of an erg, and it will 
indicate a variation of current of one sixty-millionth of an ampere.) 
Obviously the telephone can be used also with the less sensitive detector. 
A recording detector requires less skill on the part of an operator in 
the reception of signals, inasmuch as it is easier to learn to read the 
signals from a record than by sound. The telephone as a receiver has 
the advantage that in the event of interfering signals an expert opera¬ 
tor can sometimes pick out the signals from his own station, and in 
the recent yacht races in New York Harbor it is said this was actually 
done by the De Forest operators. Such signals would be unreadable 
on an ordinary strip record. This advantage of the telephone as a 
receiver was also noticed on the wireless circuit between Jersey City 
and Philadelphia by Fessenden, who points out further that when the 
interfering signals were strengthened and the Philadelphia signals 
were weakened the reading of the messages was easy; and, he adds, 
this shows that if the difference in intensity is sufficiently great, within 
limits, both sounds are readily separated. (See page 51.) 


INTERRUPTERS-TRANSFORMERS. 

Hitherto the most common method of originating the electric 
oscillations employed in wireless telegraphy has been by means of a 
Bhumkorff coil giving about a ten-inch spark. According to Flem¬ 
ing, the primary of a coil giving a ten-inch spark consists usually of 
350 turns or 300 feet of heavy copper wire about .1 inch diameter, 
having a resistance of about .35 ohm, with an inductance of about 
.02 henry. The secondary wire consists of about 10 miles of copper 



108 


WIRELESS TELEGRAPHY. 


wire .008 inch diameter, giving 50,000 turns of wire, with a resist¬ 
ance of 6600 ohms and an inductance of 460 henrys. 

Such coils, however, are giving way, in many cases, to motor- 
driven alternating current generators and step-up transformers. As 
previously noted (page 7), the ordinary interrupter of the induction 
coil is based on the principle of the electric door-bell, in which a soft- 
iron hammer carried on the end of a strip of springy metal is placed 
opposite the core of the coil (see Fig. 110). The contacts of the 
primary are carried on the spring and on a post adjacent thereto. 
This is termed a hammer interrupter, and its rate of vibration is about 
eight to twelve per second, depending somewhat on the tension of 
the spring. Owing to the comparatively strong currents employed 
(about eight amperes) in the primary circuit the contacts are rapidly 
worn, and it requires much attention to maintain them in proper 
adjustment. When currents of over ten amperes are used the plati¬ 
num contacts are apt to fuse, this rendering necessary a resort to 
other and more practicable forms of interrupters. 

As intimated elsewhere, 
the E. M. F. employed with 
this induction coil is general¬ 
ly about 10 to 15 volts. This 
is furnished usually by a pri¬ 
mary or storage battery. 
When current from street 
mains is available the voltage 
must be cut down by means 
of incandescent lamps or other suitable resistances. 

In modifications of the hammer interrupter, the primary circuit 
is broken independently of the core of the coil, as outlined in Fig. 112, 
in which p and 5 are the primary and secondary wires of the induc¬ 
tion coil i; k is a Morse key; j is a jar containing mercury; l is a 
metal arm extending from the lever L into the mercury; m is an 
electromagnet. The arrangement of the circuits is such that the 
lever l will vibrate continuously, the arm l rising out of the mercury 
at each upward motion, and thereby interrupting the circuit of bat¬ 
tery b through primary wire p when key k is closed. When that key 
is open no current flows in the primary wire. A switch is provided 
to-open the circuit of M when desired. To quickly break the spark 
when arm l leaves the mercury, and also to prevent oxidation, a layer 


nmm 


1 L 


FI 


K 


ilili 




Mm li 



Fig. 112. Mercury Interrupter. 


























MERCURY, WEHNELT INTERRUPTERS. 


199 


of water, alcohol, or petroleum is placed oil the mercury. By some 
workers petroleum is given the preference for this purpose, as it has a 
high point of ignition and evaporates but slowly. An advantage of 
the mercury interrupter over the hammer interrupter is that the break 
is more sudden; also with the former the duration of the contact may 
be made longer. Lord Rayleigh has pointed out that if the interruption 
of the circuit could be made with sufficient rapidity, as by cutting the 
wire with a bullet from a rifle, the condenser in the induction coil 
could be dispensed with; and other experimenters have obtained a 
decided increase in the length of the spark, with a given E. M. E., 
by the use of devices that cause quick breaks of the primary circuit. 
To facilitate rapid breaks for this purpose, other forms of interrupters, 
known as mercury-jet interrupters, are employed, in which a jet of 
mercury is thrown against rapidly moving metal contacts rotated by 
suitable motors. 

As another means of securing rapid breaks in the primary circuit 
of the induction coil, the Wehnelt interrupter, shown in Eig. 113, 
has been used in wireless teleg¬ 
raphy. This is an electrolytic 
interrupter, and is connected 
directly in the primary circuit 
of the induction coil, no con¬ 
denser being required. In the 
figure, J is a quart glass jar, filled 
with a solution of one part of 
sulphuric acid to eight parts of 
water. The jar is provided with 
an insulated cover which up¬ 
holds a sheet of lead /, and a glass tube t about .25 inch in diam¬ 
eter, filled with mercury. The leal sheet is nearly the width of and 
reaches almost to the bottom of the jar. A platinum wire p, No. 20 
gauge, extends outside of the tube, and is sealed in it. By turning 
the tube t the position of the lower end of the platinum wire relative 
to the sheet of lead may be readily adjusted. The upper end of l 
and the mercury in the tube are connected by clamps to a source of 
E. M. F., b, and to the primary of the induction coil I. At least 
25 volts are required to operate this cell as an interrupter. When 
the circuit of b is closed the interruptions occur at the rate of 100 to 
1700 per second, the rate of interruptions increasing with the voltage. 


o o 



Fig. 113. Wehnelt Interrupter. 






















200 


WIRELESS TELEGRAPHY. 


The efficiency of the apparatus is increased with whatever increases 
the self-induction in the circuit. Ordinarily the inductance of the 
primary of the induction coil is sufficient. An advantage of this 
interrupter is that the E. M. E. and strength of current may be 
increased beyond what would be feasible with platinum contacts of 
the ordinary contact interrupter, and in this way the output of the 
induction coil may be enhanced. Care must be taken that the tube 
does not break near its lower end, and for this reason an ebonite tube 
is preferable to glass. A number of theories have been offered to 
account for the action of this interrupter. According to Walter, when 
the current first begins to flow oxygen is formed on the positive pole, 
and the temperature rapidly rises until a layer of steam forms around 
that pole. This is sufficiently non-conducting to cause considerable 
reduction of current. The self-induction in primary thereupon pro¬ 
duces considerable increase of E. M. F.; the layer of steam is electro¬ 
lyzed into a mixture of explosive gases and is finally exploded by a 
spark. The explosion drives the liquid from the positive pole, pro¬ 
ducing thereby a rapid momentary cessation of current. 

In the majority of transmitters now employed in wireless teleg¬ 
raphy the oscillations are not only rapidly damped, but also have a 
comparatively long interval between each interruption, all of which 
reacts against successful resonance. Hence it has frequently been 
suggested that to obtain more efficient resonance the transmitter 
should be supplied with high-pressure, high-frequency currents of 
uniform amplitude. Therefore the Wehnelt interrupter, with its 
capability for rapid interruptions, would seem excellent for this pur¬ 
pose were it not for the fact that at each interruption a capacity has 
to be charged—either the aerial wire or a condenser, now usually the 
latter, which discharges its stored energy into the aerial wire. And 
inasmuch as the time of charging a condenser is roughly about seven 
times greater than the time constant of the circuit, which constant, 
in turn, is equal to the product of the resistance in megohms and the 
capacity in microfarads of the circuit, the high resistance of the 
secondary wire of the induction coil used with the Wehnelt inter¬ 
rupter places a rather low limit on the number of interruptions per 
second that can be utilized with this apparatus or any other inter¬ 
rupter employing directly : 1 induction coil. For example, if the 
resistance of the secondayv 1 \ rev, 10,000 ohms (equal to .01 megohm) 
and the capacity of the ci r- t be .02 microfarads, the time constant 


TIME CONSTANT—HEWITT INTERRUPTER. 


201 


will be .0002 seconds, and the time during which the maximum 
E. M. F. should be applied to properly charge the condenser should 
be approximately one five-hundredth of a second, which would limit 
the number of interruptions in such a circuit to about 500 per 
second. There is, besides, the time of total charging and clearing 
out, which still further reduces this limit. 

The mercury-vapor interrupter, which is a modification of the 
Hewitt mercury-vapor lamp, has also been proposed as available in 
wireless telegraphy to secure the desired resonance, because of the 
high rate and uniformity of its interruptions, but thus far it has not 
gone into practical operation. This interrupter is indicated at v, 
Fig. 114. It consists of a glass globe, at the bottom of which two 
tubes t t are sealed in. 

These tubes are partially 
filled with mercury. The 
connections for this inter¬ 
rupter as arranged for wire¬ 
less telegraphy are shown in 
the figure, in which D is an 
alternating current genera¬ 
tor and t is a transformer 
for raising the potential to 

10,000 or 14,000 volts, as desired. The interrupter here takes the 
place of the ordinary spark-gap and with the condensers c c and in-^ 
ductance p form the oscillating circuit. This inductance, with the 
other portion s of the coil, also constitutes an auto-transformer 
corresponding to that shown in Fig. 98 a. In the operation of the 
Hewitt vapor-lamp it is found that the negative electrode offers a very 
high resistance to the passage of current through it until the E. M. 4. 
reaches a certain critical value, say 10,000 to 14,000 volts, when this 



resistance suddenly collapses, whereupon current flows through the 
lamp or tubes. When, however, the E. M. F. now falls to a small 
value, the initial cathode (negative pole) resistance again instantly 
becomes operative, stopping current flow. When arranged as in the 
figure, the transformer charges the condensers during the short time 
that the cathode high resistance exists. As soon as this resistance 
falls as stated, the condenser discharges itself through the globe, set¬ 
ting up rapid oscillations in the aerial wire or other circuit, the 
rate of which is regulated at will by varying the capacity cc or 
inductance I. This interrupter differs from the ordinary spark-gap 












202 


WIRELESS TELEGRAPHY. 


in that when the half-period of the transformer is nearly complete, 
and thus the current is nearly at its zero value, the cathode resistance 
comes into play until the condenser is again charged. In this way, it 
is pointed out, a succession of rapid-current impulses, separated from 
each other by small intervals of time, is obtained; these time inter¬ 
vals depending on the rapidity with which the transformer can 
recharge the condenser after each disruptive discharge in the tubes. 
It has been estimated that with sufficiently high power in the dynamo 
and transformer the current impulses may be made to occur at the 
rate of several millions per second. In experiments described by the 
inventor, in which a small alternator of about 2 kilowatts, was em¬ 
ployed and in which the capacity of the condensers was .015 micro¬ 
farad and the diameter of the secondary coil n was 38 inches, a rate 
of discharge of one riiillion per second was secured. This interrupter 
if markedly efficient, there being a drop of but 14 volts at all pres¬ 
sures in the tube; this loss of energy being used in vaporizing the 
mercury which condenses on the walls of the globe and runs back 
into the mercury receptacles, thereby assisting in cooling the globe. 

Another interrupter, somewhat analogous to the foregoing, which 
has also been proposed for wireless telegraphy is known as the musical 
arc, due to W. Duddell, and described in British patent No. 21,629. 
Briefly, this interrupter is one in which a direct current is supplied 
to an arc lamp which is in parallel with a capacity and inductance. 
Under proper adjustment of the capacity and inductance rapidly 
alternating currents are set up. 

The need of greater radiating power in long-distance transmission 
has, as already mentioned, led to the adoption of special oscillating 
inductors and transformers, of which examples have been given in the 
preceding pages. The transformers used by Marconi, De Forest, and 
others range in capacity from one kilowatt or less to fifty or more 
kilowatts, and transform the E. M. F. of the generator to 25,000 or 
50,000 volts, as required. The frequency of alternations of the trans¬ 
former depends on the design and frequency of the generator. The 
generators used by the International Wireless Telegraph Co. are 
operated at 60 cycles per second and have an output of 40 amperes 
at 100 volts. 

A special form of induction coil now used in wireless telegraphv 
is about four feet in length. The iron core is made up of iron wires 
four feet long, forming a bundle about three inches in diameter. The 


INDUCTION COILS—OSCILLATORS. 


203 


primary wire is composed of No. 16 copper wire measuring about 
7 ohms. This is wound over the iron core, one terminal coming out 
at one end of the core, the other terminal at the other end. A tube 
of hard rubber, half an inch thick, is placed over the primary core 
from end to end. The secondary is wound outside of the primary 
in two sections, each section being composed of fine wire measuring 
about 6000 ohms. The finished coil is about ten inches in diameter. 
The completed coil is placed in a box which is filled with a liquid wax 
which speedily hardens to the consistency of resin. The primary 
terminals are connected to a generator giving current at a desired 
voltage and rate of alternation, which is raised to a higli voltage at 
the secondary terminals, in some cases 20,000 to 40,000 volts. 

The arrangement of coils and condensers forming an oscilla¬ 
ting circuit, in which the condenser is charged by the secondary 
of a transformer or an inductance coil, and which condenser in turn 
discharges into the primary of another transformer, is sometimes 
termed the Tesla high-frequency coil. (See U. S. patent No. 454,622.) 

A form of 10,000-volt induction coil or transformer made by 
Mr. W. J. Clarke, of New York, consists of a core composed of well- 
rusted soft-iron wire, No. 14 gauge, 14 inches long and 3.5 inches in 
diameter. Over this coil is wound 326 feet of No. 11 copper wire, 
or about three and one-eighth turns per volt. This coil and core are 
secured vertically on a thick wooden base by bolts. Its terminals are 
brought to clamps on the base. The secondary is wound on a paper 
tube 4.125 inches in diameter, and is composed of 56,000 feet of No. 32, 
wire, laid up in .25-inch sections, the walls of which are well insulated. 
This coil slips over the primary bobbin, and may be removed or 
replaced by another coil at will. This coil, when connected to a 104- 
volt alternating circuit, delivers 10,000 volts at the secondary; or it 
may be connected up with a mercury or Wehnelt. interrupter. 

A form of oscillator that may be employed in wireless telegraphy 
consists of a primary wire of one turn of half-inch tubing, brass or 
copper, arranged as a square with 50-inch sides. The secondary is a 
flat spiral of 110 turns of No. 18 B. and S. copper or brass wire, 
placed on a board or other suitable supports, the turns being well 
separated. The primary is placed five inches below or at the back of 
the secondary. The secondary is in series with a spark-gap and a 
10-by-l2-inch glass-plate condenser, adjustable by removing or add¬ 
ing plates. When the primary is connected with the secondary of 


204 


WIRELESS TELEGRAPHY. 


an induction coil giving 10,000 volts of GO cycles per second, a beau¬ 
tiful 15-inch spark may be drawn from the center terminal into the 
air, the outer terminal being to ground. A 12-inch spark may be 
obtained between the inner and outer terminals. This coil is also 
manufactured by Mr. Clarke. 

M. Lebedew and M. Bose devised an oscillator capable of pro¬ 
ducing oscillations the wave-length of which is not more than .23 inch. 
It comprises two cylinders of platinum .05 inch long and .019 inch 
in diameter, each placed in a glass tube with their sparking ends 
facing each other. Wires, in which is a condenser, connect the cylin¬ 
ders to the induction coil. This oscillator is placed on the focal line 
of a small cylindrical mirror having a focal length of .23 inch. The 
mirror and oscillator are immersed in oil. 


SPARK-GAP—CONDENSERS—ANTENNiE. 

With comparatively small transformers only the ordinary precau¬ 
tions are necessary at the spark-gap to avoid short-circuiting; but 
when powerful transformers are used it is found that when the points 
are brought too close together an arc is formed, which tends to short- 
circuit the secondary circuit of the transformer and thereby give rise 
to heavy currents in the primary circuit. Even a partial short-cir¬ 
cuiting stops the oscillations in the condenser circuit. As it is not 
permissible to increase the length of the spark beyond a certain point, 
owing to the resistance which this would introduce, various other 
means are employed to obviate this arc, some of which have already 
been noted, namely, the placing of a strong magnetic field trans¬ 
versely across the gap, also the use of an air-blast, which devices blow 
out the arc but do not prevent the operation of the oscillating sparks. 
(The air-blast also tends to keep the discharge points cool.) Flem¬ 
ing avoids this arcing by a certain arrangement of the magnetic coils 
in the primary circuit of the transformer of his transmitting circuit. 
Other experimenters have shortened the spark-gap while retaining a 
high E. M. F. by the use of compressed air or gases around the spark- 
balls or points. Fessenden, for instance, has found that an E. M. F. 
capable of giving a four-inch spark in ordinary air would only give 
a quarter-inch spark when the electrodes were placed under a pres¬ 
sure of 50 pounds to the square inch. He further found, by con¬ 
necting a radiator of electric waves to one of the spark-balls, that up 



SPARK-GAP—CAPACITY EFFECTS. 


205 


to a pressure of 50 pounds per square inch the radiation was not 
improved, but above that pressure the radiation was greatly enhanced. 
For instance, at 80 pounds pressure the radiation was increased three 
and one half times, the E. M. E. being the same in each case. 

The maximum length of the spark-gap employed in wireless teleg¬ 
raphy is about one inch. For high electromotive forces brass rods 
about live eighths of an inch in diameter, blunted at the sparking 
ends (in some cases tipped with aluminum or zinc), are now quite 
frequently used at the spark-gap. For transmitters employing two 
or more kilowatts, multiple spark-gaps are sometimes provided to dis¬ 
sipate the heat, and curved discs or adjustable balls, amongst which 
the spark is divided, are utilized for this purpose. 


To an experienced attendant the character of the spark is an 
index of the nature of the oscillations, and hence of the radiation, 
and he soon acquires the ability to adjust the length of the spark-gap 
and the amount of inductance and capacity necessary for best results 
from the general appearance of the spark. If the capacity is too 
small for the transformer or other source of energy, the spark will be 
yellow and flaming, like an arc. If too large, the length of gap must 
be decreased and spark will then be intermittent and irregular. With 
capacity constant the spark becomes fat and white as the inductance 
of the antenna oscillating system is cut out, and blue and stringy as 
inductance is added. 

It has been found advantageous in practice by some workers to em¬ 
ploy in the oscillating circuit an excess of capacity over inductance 
in long-distance transmission. Lord Rayleigh, however, has shown 
that if the capacity of a radiating system exceeds a certain critical 
value its efficiency is diminished very materially. Actual experiments 
by Shoemaker have indicated that an excess of capacity in the oscil¬ 
lating circuit gives a curve of potential on the antenna that increases 
slowly till near the top, when it widens out abruptly. An excess of 
inductance gives a small loop of potential at the top, while equal 
inductance and capacity give a practically uniform curve, but a 
smaller maximum potential. The experimenter employed two long 
metal rods laid horizontally, to one of the terminals of which he con¬ 
nected an oscillating circuit. He bridged these rods at the first node 
of potential, as in the Lecher system of wires. Beyond this bridge 
he moved a stiff wire, one end of which was allowed to rest trans¬ 
versely on one of the rods, while the other end was approached to 


206 


WIRELESS TELEGRAPHY. 


the other parallel rod, measuring the length of the spark obtained as 
the wire was pushed along the parallel rods, when the results stated 
were obtained. 

Professor Seibt shows the variation of potential in a wire by the 
following arrangement, Figs. 115 and 116, in which p s are the coils 
of a transformer T with an adjustable oscillating circuit s, L, c , c. 



A long coil of fine wire w is wound on an insulated wooden rod six 
feet long and two inches in diameter, and is connected at its lower 
end to the oscillating circuit, as indicated, to' is a single wire held 
parallel to the coil w and earthed. When the inductance and capacity 
of the oscillating circuit are made to correspond with that of the 
natural periodicity of the coil w, luminous discharges may be seen to 
occur between the coil w and the grounded wire w\ the brightness of 
which increases with the potential, along the wire, which in the case 
in point would be as represented by the dotted lines in Fig. 115. 
If the period of the oscillating circuit is increased by varying the 
inductance and capacity of c, as by putting the condensers or jars in 
series, the wave-length is shortened as indicated by dotted lines in 
Fig. 116, which results may be varied at will by suitable arrangement 
of the inductance and capacity. 

M. G. Ferrie describes a method which he employs to determine 
the wave-length of the oscillations produced in a vertical wire. He 
connects a horizontal wire to the vertical wire at a point between 
the oscillator and the ground. In the horizontal wire he places a 
hot-wire ammeter, which indicates by the movements of its pointer 
the amplitude of the oscillations. Then by varying the length of the 
horizontal wire, the amplitude of oscillations will vary between a maxi- 











































CAPACITY OF VERTICAL WIRES. 


207 


mum and a minimum: the maximum occurring when the wire is in 
tune with the oscillations. By this means the fundamental oscillation 
period as well as the harmonics of the oscillating system can be 
ascertained. (See Wave-meters, Appendix, p. 311.) 

The main object, as previously intimated (page 48), in employing 
a number of vertical wires has been to obtain increased capacity 
wherein to store electrical energy to be radiated as electric waves, the 
vertical wire serving as one plate or plates of a condenser, the earth 
as the other, and the air as the insulating medium. The capacity of 
a vertical wire is obviously not uniform throughout its length, but 
decreases with its distance from the earth. Hence with a given 
charge oscillating in the wire, the potential at given points in the 
wire will increase as the capacity diminishes (see Lecher system of 
wires, p. 145), which will add somewhat to the amplitude of the 
potential loop at the top of the vertical wire, assuming a wave-length 
equal to four times that of the length of that wire. Fleming gives 
the capacity of a vertical wire .1 inch in diameter and 100 feet long, 
with its lower end 6 feet from the earth, as .0002 microfarad. It has 
been found that, owing perhaps to an opposing effect of mutual 
induction, the wires being charged with similar polarities, the effec¬ 
tive capacity of adjacent parallel vertical wires is not equal to that of 
a similar number of widely separated single wires, but, according to 
tests by the authority just quoted, is about equal to the square root 
of the number of wires. He also points out (“Popular Science 
Monthly/’ August, 1903) that to store up a definite amount of elec¬ 
tricity in a condenser, a certain definite amount of dielectric is re¬ 
quired, regardless of how it is arranged. Thus, suppose a glass conden¬ 
ser of .0027 microfarad capacity, the dielectric of which is 12 inches 
square and .03 centimeters thick, giving a volume of 270 cubic centi¬ 
meters, charged by 20,000 volts. The energy stored in the shape of 
electric strain is .5 joule. To store up one joule (equal to .7373 foot¬ 
pounds) would require 520 cubic centimeters of glass. In the case of 
air-condensers the energy storage is much less, being about one foot¬ 
pound per cubic foot or volume. 

From a description of one of the Marconi station equipments, 
Koepsel has calculated there must have been a wave-length of 8528 
feet, which would require a wire 1968 feet long to secure good reso¬ 
nance. The wire being only 295 feet in length, Koepsel assumes 
that the system of 400 vertical wires employed is necessary to shorten 


208 


WIRELESS TELEGRAPHY. 


the resonance when such large capacities and wave-lengths are iised ? 
and not for the purpose of increasing radiation into space. 

The condensers for the transmitting circuits in wireless telegraphy 
are a very important part of the equipment. Generally speaking, 
Leyden jars are used for installations up to one or two kilowatts, owing 
to convenience of handling, cleanliness, etc., but for installations 
using more than two or three kilowatts glass-plate condensers are fre¬ 
quently utilized by Marconi, De Forest, and others (see page 66). 
The plate-glass condensers used by De Forest are 30 inches long by 
15 inches wide, and are .25 inch thick. Tin-foil is so placed on each 
side of the plate as to leave a margin of four inches all around except 
at the connecting point. It is essential to thoroughly paste or glue 
the tin-foil to the glass to exclude air. The plates are generally 
immersed in a good quality of linseed oil, although some users of 
plate-glass condensers have obtained satisfactory results without oil. 
Domestic glass plates of the dimensions stated cost one dollar each. 
Imported German plates of the same size cost three dollars each in 
this country. The thickness of glass for this purpose should be at 
least one-tenth inch per 20,000 volts. The jar condensers used by 
Shoemaker are 16 inches high by 5.25 inches in diameter, and are 
specially made to withstand the pressures to which they are subjected, 
having a maximum thickness of .25 inch and a minimum of three 
sixty-fourths inch. Their cost is about seventy cents per jar. These 
jars have a capacity of .004 microfarad. In practice they have been 
found very durable, but ordinarily Leyden jars lose their efficiency 
after comparatively short service, owing to deterioration of the tin-foil 
due to brush discharges and sparking. The glass-plate condensers 
have the advantage as regards bulk. Where brush discharges must 
be eliminated to obtain sharp tuning and resonance, the use of plate- 
glass condensers in oil appears to be imperative. As inductive effects 
are proportional to the frequency, which in wireless telegraphy is 
high, inductance should be diminished wherever possible. To that 
end the length of the connecting wire should be the same to each 
condenser or jar (p. 66). When it is desired to avoid dielectric hys- 
teresis metal plates with air as the dielectric are employed. 

A number of different arrangements of the antennae employed in 
wireless telegraphy have already been shown. In the Shoemaker sys¬ 
tem a latticed wooden tower supports the wires. From the top of a 
tower 160 feet in height, four well-insulated arms are projected. Each 
of these arms carries six No. 14 wires (held apart by spreaders), which 
drop vertically to within 15 or 20 feet of the earth, where they are 


ARRANGEMENT OF ANTENNAE. 


200 


unitedly led into the instrument-room. In some of the recent inland 
stations of the Marconi company, as, for instance, at the 90-mile cir¬ 
cuit between Milwaukee and Chicago, 15 wires are supported from 
one mast, as follows: The wires are suspended in series of five from 
the top of the mast, from which they are well insulated. The wires 
of each series are about 10 or 15 feet apart in the middle; each series 
is separated by a distance of 50 or 60 feet. Each wire of a series is 
attached at a distance of about 50 feet from the top of the mast M 
(Fig. 117) to a guy-rope r, which latter is attached to an anchor- 
post a in the earth, 40 feet or more from the 
base B of the mast. At its point of connection 
with the guy-rope each wire is drawn toward the 
foot of the mast, where all the vertical wires 
converge and are led into the operating-room. 

The wires thus form a > with the mast as a 
base, and, being held well apart from one another, 
mutual static induction is measurably avoided. 

No spreaders are required. The mast at the Mil¬ 
waukee station is situated about one-quarter mile 
from the lake shore. The station itself consists 
of a one-room wooden building about 18 feet 
long, 15 feet wide, and 10 or 12 feet in height, 
with an extension somewhat smaller, the latter 
containing the oil engine and generator. 

At Fessenden’s Jersey City station, 20 wires, 
about No. 16 gauge, are suspended from a long 
wooden strip which is upheld by petticoat insulators supported by a 
rope between the tops of two masts about 150 feet high and 80 feet 
apart. The wires, two feet apart, drop vertically to a similar wooden 
strip, held parallel with the upper strip, where the wires are con¬ 
nected together and led into the hut through a bushing in a large 
plate-glass window. 

As a means of elevating the vertical wire, kites and captive bal¬ 
loons have been proposed from the earliest days of the art of wireless 
telegraphy, and have frequently been used for temporary work. As 
pointed out by Marconi, the varying height of a kite would detrimen¬ 
tally affect the operation of syntonized systems. Edison, in his patent 
of 1891 on wireless telegraphy, proposed the employment of balloons 
for this purpose. The inclination of the angle of the vertical wires 
has been found not to make much difference in the results obtained. 





210 


WIRELESS TELEGRAPHY. 


but it must not exceed 40°. The material of the vertical wire does 
not appear to be very important except as regards strength, weight, 
and durability. As elsewhere remarked, the insulation of the vertical 
wires is very important, and some of the devices by which proper 
insulation is obtained have been noted. Metal and rope guy wires 
should be carefully insulated from the ground and mast. De Forest 
advises insulating iron guy wires in sections. According to Zenneck, 
a second vertical wire as long as the transmitting wire, erected 
near it and connected to earth, intercepts the electric waves, and 
hence prevents them from reaching distant stations in that direction. 
Braun has found that two vertical wires receive signals only when 
their planes nearly coincide with the direction of the incoming waves. 
In this way he notes the bearing of the sending station may be deter¬ 
mined to within 10°, a result of special importance for nautical and 
military purposes. 

The need of a good earth in wireless telegraphy has been found 
by most experimenters to be as essential as in wire telegraphy. This 
seems to be especially the case at the sending end, although in receiv¬ 
ing also an improved earth connection has often resulted in improved 
signals. Mr. H. B. Jackson has found in the course of a number of 
experiments that the absence of grounding in the receiver reduced 
the signaling distance 50 or 70 per cent., and the absence of a ground 
in the transmitter, 85 per cent. The investigations of Professor 
Tanakadate have shown that large capacity in an earth plate is more 
important than merely good conductance, and therefore, that plates 
arranged in strips are superior for this purpose to square plates. To 
this end, probably, Marconi in some of his stations uses a long strip 
of metal inserted edgewise in the earth and projecting about one foot 
above the surface of the earth. Wires are run from various parts of 
this plate to the apparatus. De Forest in some cases uses a sheet of 
copper thirty feet long and four feet wide imbedded two or three feet 
in the earth, giving about 240 feet of surface. When practicable, 
the ground plate is sunk in the sea, which connection is considered 
by some workers to be the best. On shipboard, as previously noted, 
the earth is secured by attaching a wire to the bolts of the iron frame 
of the vessel. The experience of Braun in using capacity plates not 
directly connected to earth appears to be at variance with the expe¬ 
rience of other workers, and hence it is thought that the capacities 
he employs are only apparently independent of the earth. It is under- 


GROUNDING OF ANTENNiE. 


211 


stood that in some of the latter installations of the Braun system a 
ground is employed. Jackson, in the experiments referred to else¬ 
where, found that a condenser of suitable capacity acts nearly as well 
as a ground. Guarini also transmitted signals between Brussels and 
Malines, in 1901, without a ground connection. 

As noted on page 121, Professor Fessenden employs a wave-chute 
or artificial ground at the lower end of the antennae. This chute may 
consist of a number of wires all connected together by transverse wires, 
or of a strip of metal; and where the waves are cut off by high build¬ 
ings or high trees, this conductor should be extended until it passes 
beyond the limits of the obstacle and there grounded. This form of 
ground insures that the conditions near the antennae shall be prac¬ 
tically similar in all kinds of weather; and the inventor cites an 
instance where, without such an artificial conducting surface on rocky 
shores, the salt spray in stormy weather sometimes renders the ground 
surface near the antennae conducting, while in fair weather it is insu¬ 
lating. He has found that even a few ohms resistance in the ground 
connection renders it impossible to send signals unless the artificial 
conducting surface is also present. In practice, the wires composing 
the wave-chute consist of ten or twelve galvanized iron wires, about 
Ho. 8 gauge, which, in the absence of buildings, extend along the 
surface of the earth for a distance of 100 feet or more, in the direc¬ 
tion of transmission, when the wires are separately grounded by con¬ 
tact with metal rods stuck in the earth. M. Blondel does not consider 
this addition of a metallic conductor of half a wave-length under the 
vertical wires necessary, a large capacity or metallic earth-plates there 

sufficing. 

In recent experiments in the vicinity of Detroit, Mich., Mr. T. E. 
Clark uses a large capacity at foot of a 65-foot transmitting aerial, not 
grounded, to avoid, as he states, overloading one side of the oscillator 
coil, and has obtained good results through a distance of twelve miles 
over a hilly, wooded country. The current strength in the primary 
wire of the induction coil is 1 ampere at 110 volts, direct current, 
broken by a magnetic vibrator in series with a liquid interrupter giv¬ 
ing a high rate'’of interruptions. Spark-gap .25 inch. A hot-wire 
ammeter shows 1 to 1.3 amperes in transmitting antenna. A filings- 
coherer is used in series with a grounded vertical wire at the receiv- 

ing station. 


212 


WIRELESS TELEGRAPHY. 


LAND AND SHIPBOARD AERIALS—ALTERNATING CURRENT RECTIFIERS AS 

WIRELESS DETECTORS-THE SILICON, PERIKON, CARBORUNDUM, 

VALVE AND OTHER DETECTORS—SENSITIVENESS OF DETECTORS, 

ETC.-HOT WIRE AMMETER-ALLSTROM AND SULLIVAN RELAYS- 

TRANSFORMERS-COUPLING-TUNING COILS—VARIOMETERS, ETC. 

Since the foregoing sections in this chapter were written (1902) 
numerous improvements in the devices mentioned therein have been 
made, as well as many additions to the general knowledge concerning 
the same, a reference to some of which follows. 

Land and Shipboard Aerials.— In Fig. 1 herewith are shown vari¬ 
ous ways in which two or more aerial wires may be arranged as an¬ 
tenna. A single wire as aerial is now rarely used. The wires may 
be of varying length depending on circumstances. In the figure a 




Fig. i.—Some Forms of Aerials. 

indicates two wires which may be open or closed at top; c represents 
a 4 wire arrangement, of which there are many variations ; f is a cage 
arrangement consisting of 4, 6 or more wires, in which the wires are 
held apart by hoop frames; g is a box method in which the wires are 
separated by a suitable wooden frame. The arrangement of wires 
shown at c, or modifications thereof, is the one most generally adopted. 
These wires are usually held apart by wooden spreaders at top and 
bottom, and at the middle if the wires are very long, a' represents an 
“Eddy” kite arrangement for supporting the aerial; two or more of 
these kites may be used in tandem. 
































SHIPBOARD AERIALS. 


213 


On shipboard when the available masts are comparatively low it is 
essential that the number of aerial wires be increased to obtain ca¬ 
pacity in the radiating system. This is done in numerous different 
ways. In some instances the wires are assembled in the cage from f, 
Fig. 1, in which the wires are held up by suitable supports to the 
masthead, from which the wires are carried, more or less obliquely, to 
the operating room. In other cases again the wires in cage or box 
form are suspended between the tops of two masts, and vertical wires 
are dropped from the horizontal wires to the deck. 

A form of aerial largely used on shipboard and at shore stations 
is that known as the t or l aerial. An instance of an l aerial is out¬ 
lined in Fig. la, in which 6 horizontal wires w are supported be¬ 
tween 2 masts and from which wires 6 vertical wires w, held apart 



by wooden spreaders s, are dropped to a point near the deck, where 
they converge and after being cabled are led into the operating room 
c in any of the usual ways. (See page 60, rat-tail plan.) In a t aerial 
the vertical wires would be attached to the center of the horizontal 
wires, as at x, instead of at one end of the wires. In the l arrange¬ 
ment the horizontal wires which add capacity to the aerial, and pos¬ 
sibly give a directive effect to the radiated waves, are joined together 
at the far end. In the t arrangement the ends are also usually closed. 
Frequently only 2 vertical wires w are used instead of 6 in connection 
■with t and l aerials, one vertical wire being connected with, say, 3 
horizontal wires in this case, on the looped aerial plan. In Fig. 2, 
which indicates the aerial of a recently equipped battleship, the height 
of the masts is about 65 feet; the distance between masts is 200 feet. 
The aerial wires are composed of strands of 7 No. 18 phosphor-bronze 































214 


WIRELESS TELEGRAPHY. 


wires to insure adequate mechanical strength. The horizontal wires 
are supported by means of slender and corrugated insulators r, about 
2 feet long, formed of an insulating material termed “electrose,” and 
are attached to the masthead m by suitable tackle t, which in turn 
upholds a thick spar p, 15 feet in length, to which the insulators are 
fastened. The horizontal wires are 2.5 feet apart. 

In some of the more recently constructed Marconi trans-Atlantic 
aerials the l arrangement, or bent antenna, is employed, virtually as 
outlined in Fig. la, except that more and larger horizontal wires are 
employed which are upheld by suitable masts. (See Bent Antenna, 
Directive Wireless Signaling, Chapter XVI.) 

At the Brooklyn Xavy Yard wireless station a t aerial consisting of 
10 horizontal and 10 vertical wires are utilized. The wires are sup¬ 
ported between 2 masts 180 feet in height and 300 feet apart. The 
actual length of the horizontal wires is 200 feet. They are about 2.5 
feet apart, and are attached at both ends to wooden spars 27 feet long, 
which spars in turn are upheld by suitable insulating devices at¬ 
tached to the top of the masts. The aerial conductors are composed 
of 7 No. 20 phosphor-bronze wires. The vertical wires are brought 
down to the side of the operating room in 2 sets of 5 each, held apart 
by spreaders, whence each set of wires is led into the operating room 
by a cable composed of 10 conductors each of 7 No. 24 wires. This plan 
admits of the use of a looped or straight aerial, as may be desired. A 
15-kilowatt Stone wireless outfit is installed at this station. There is 
also a 5-kilowatt Telefunken system in operation at this Navy Yard. 


Alternating Current Rectifiers as Wireless Detectors. — It was at 

first believed that the operation of the well-known silicon and cer¬ 
tain other detectors was based on a thermo-electric action, by which 
the presence of heat developed by the electric current at the junction 
of two dissimilar conductors gives rise to an e. m. f. at the said junc¬ 
tion, or couple. Subsequent experiments by Pickard apparently 
demonstrated, however, that the operation of this and many other sub¬ 
stances tested was due to a current rectifying property and not to a 
thermo-electric effect. In other words, that the effect is due to a 
property of certain minerals, by virtue of which they conduct a cur- 



CURRENT RECTIFIERS. 


215 


rent of electricity in one direction only, or at least to a greater extent 
in one direction than the other. No satisfactory explanation of this 
action has yet been advanced. Fleming has suggested that homo¬ 
geneous conductors may he considered to give free passage to elec¬ 
trons, while compound substances may exclude or admit them by a 
system of valves, and that possibly in a crystallized substance all the 
valves may face in one way, thereby facilitating the drift of electrons 
in one direction while opposing their movement in the other direction. 
(See page 42 herein, also Cassier’s Magazine, Sept., 1908, page 461.) 

This rectifying property of minerals was probably first noticed by 
Ferdinand Braun (Poggendorf Annalen, 153, 1874, page 550). In 
his experiments Braun employed the mineral tetrahedrite in a circuit 
containing a potentiometer, a battery, galvanometer and pole-changer. 
Contact was made with a crystal of the mineral by means of 2 silver 
wires with rounded ends. Changing the direction of the current in 
the circuit a much larger deflection of the galvanometer was ob¬ 
tained with one polarity than the other; in one instance in the ratio 
of 3 to 1. That this result is not due to thermo-electric action ap¬ 
pears evident from the fact, as noted by Braun, that using an im¬ 
pressed e. M. F. of 15 volts certain minerals have shown a unilateral 
conductivity much higher than can be satisfactorily accounted for by 
thermo-electric action. 

Early in Pickard’s investigation of this subject he discovered that 
for the obtainment of satisfactory results one of the terminals of the 
current rectifying conductors must not only have a perfect contact, 
but must also have a large area; otherwise the rectification will be 
irregular if not altogether absent, due to the second contact, which if 
of small area, itself acts as an opposing rectifier, thereby reducing or 
neutralizing the observable rectifying action. 

It is known that there are numerous automatic alternating (or os¬ 
cillating) current rectifiers. For instance, electrolytic rectifiers such 
as the aluminum rectifier in which an aluminum electrode in a suit¬ 
able’ electrolyte is opposed to a platinum or lead electrode. Or gase¬ 
ous rectifiers such as the Elster-Geitel tube (developed as a wireless 
detector by Fleming). Pickard proposes to apply the term “solid” 
rectifiers to the mineral types to distinguish them from the electrolytic 
and gaseous rectifiers. 

Of all the solid rectifiers tested by Pickard there are but three 
which have proven commercially satisfactory as detectors, namely, 


216 


WIRELESS TELEGRAPHY. 


silicon, zinc oxide (perikon) and molybdenum sulphide; the most effi¬ 
cient of which he states is the perikon. Molybdenum in appearance 
resembles lead, but is a softer substance which may somewhat affect 
its utility as a detector in practice. Used as a detector of electric 
waves solid rectifiers permit but one-half of the wave to pass, con¬ 
sequently giving rise in the telephone circuit to pulsatory currents in 
one direction and to which the telephone receiver is responsive. These 
current rectifiers require no extraneous battery, the e. m. f. for the 
operation of the telephone receiver being supplied by the incoming 
oscillations, rectified by the detector. It is sometimes found, how¬ 
ever, that a small local e. m. f. of the proper polarity materially im¬ 
proves the received signals; the polarity of the battery being arranged 
to co-operate w r ith the rectified current. This is apparently due to the 
fact that at zero potential the conductance of these detectors is low 
and further that the rapid change or critical point of conductance is 
confined to a range of a few tenths of a volt. In the case of the 
perikon detector the resistance was found to be 25,000 ohms at zero 
potential; also that this detector is brought to its most efficient con¬ 
ductance point with .1 volt due to the local battery. In the case of 
the silicon detector the most efficient or critical potential of the local 
battery is .15 to .2 volt; the direction of current therefrom being ar¬ 
ranged to flow from the silicon to the brass point. In the case of the 
perikon detector the current should be arranged to flow into the 
zincite at a potential of from .05 to .1 volt. Further, the most effi¬ 
cient potential of this local battery is slightly higher for strongly 
damped than for persistent trains of oscillations. The critical e. m. f. 
is found by means of a potentiometer across the terminals of the local 
battery. (See Potentiometer, Chapter XVII.) 

The Silicon Detector.— The discovery of the utility of silicon as a 
wireless detector is due to Mr. G. W. Pickard. (IT. S. Patent No. 
836,531.) The best arrangement of this detector consists in the em¬ 
ployment of a small piece of silicon of hemispherical shape, the 
round surface of which is embedded in a fusible substance such as 
solder in a metal cup to provide the large area mentioned; the other 
electrode is a piece of pointed metal impinging under pressure on the 
flat surface of the silicon. But a fragment of silicon simply held 
with suitable pressure between 2 flat ended brass rods gives excellent 
commercial results. The junction of the silicon and other metal 
should be a practically perfect electrical contact; hence the degree of 


SILICON DETECTOR. 


217 


pressure with which the two elements are joined is of much impor¬ 
tance in this detector. The silicon detector is highly sensitive, approxi¬ 
mating in that respect to the electrolytic and the magnetic detectors. 
Its sensitiveness is not impaired by severe static discharges, nor is it 
affected by humidity or variations in external temperatures. It is 
durable and inexpensive. For best results, however, the purest sili¬ 
con is recommended. Any impurities in the silicon produce inopera¬ 
tive spots on the polished surface which necessitates moving the metal 
point to find a sensitive spot. Much of the commercial silicon con¬ 
tains a certain quantity of metallic calcium, and as this metal is 
quickly attacked by air a film of calcium hydroid soon covers the sili¬ 
con surface and, according to the inventor, practically all detector 
action cases. 

In Figs. 2 and 2 a are shown different arrangements of the silicon 
detector. In Fig. 2 a brass point p is held against the silicon n by 
the pressure of a stiff helical spring h, which is adjustable by a screw. 
The pressure of the spring is varied until best results in the telephone 
are obtained. In Fig. 2 a, w is a flexible metal strip carrying at one 
end the brass point p, which is caused to rest with a constant pressure 
on the silicon surface n, which pressure is adjustable by the spring h 
as indicated. 



Fig. 2. 



Fig. 2a. 


A 



Fig. 3 - 


A conventional wireless receiving circuit including a silicon de¬ 
tector is shown in Fig. 3. a is the vertical wire; l the tuning in¬ 
ductance ; c c' are condensers; t is the telephone receiver; p a brass 
point and n the silicon element of the detector. 

The Perikon or Zincite Detector.— According to Mr. Pickard, to 
whom the detector is due, it is twice as sensitive and more easily ad¬ 
justed than the silicon detector, and constitutes the most efficient 
means known of operating the telephone without extraneous energy 
(local battery) by means of high frequency electric waves, by con- 












218 


WIRELESS TELEGRAPHY. 


verting a large proportion of the energy of the received oscillations 
into a direct current suitable for operating that instrument. (See 
U. S. Patent 886,154.) This detector is of the valve or rectifier 
type. Its elements are a fragment of zinc oxide, or zincite, and 
chalcopyrite (a copper-iron sulphide), the operative element of which 
is the zincite, held in contact under pressure. The detector is up¬ 
held by a suitably stand and is placed in series in the receiving oscil¬ 
lation circuit with the usual telephone, and might take the place of 



the silicon detector in Pig. 3; in which case p would be the Rectifying 
terminal,” or chalcopyrite, and n would be the zincite, or rectifying 
conductor. In practice the piece of zincite used p y Fig. 4, is about 
halt an inch wide across its face and is not of uniform dimensions. 

It is embedded in a ring f, of fusible 
metal held in a brass receptacle r, 
about one inch in diameter; the fusi- 
iQ\ ble metal being provided as in the 
case of the silicon detector to furnish 
large area. A blunted point of chal¬ 
copyrite c is held by a sleeve m 

Fia>. 4 .—Perikon Detector. against the rough face of the zincite 
by means of a spring s, the position of the chalcopyrite point against 
the zincite being adjustable by moving a handle h of a swivel joint ft 
pivoted at i on the base 6. 

The Carborundum Detector.— The discovery of carborundum 
as a self-restoring detector, of electric waves is assigned to General 
G. H. C. Dunwoody, late of the United States Signal Corps. As its 
name implies this detector consists of a crystal k, Fig. 5, of carborun¬ 
dum, held edgewise between 2 flat metal surfaces m m, with a 
pressure that may be regulated by screw s. 

The substance carborundum is the product of a combination of 
salt, sand, sawdust and coke, fused at a temperature of about 7,000° F. 
in an electric furnace. At low temperatures carborundum has a 
very high electrical resistance, which, however, decreases rapidly under 
heat. As but a very small area or edge of the crystal is in contact 
with the metal surfaces (estimated at less than one-billionth of a 
square inch), it is assumable that even the comparatively minute 
oscillations due to arriving wireless signals acting on such a small 
mass would produce observable variations of resistance and conse¬ 
quently variations of current strength perceptible in the telephone 
receiver. This detector, like the electrolytic and certain other de- 


















DETECTORS. 


219 


/? i «? 

U/VWA)WVWVW>^\ 

e» 

, <K<rn 

\t * 



T, 

Fig. 5. 


Wf- 



tectors, has been found to give best signals at a critical potential of 
the local battery b, which potential is obtained by varying the sliding 
contact of the potentiometer p. Pickard’s ex¬ 
periments have shown that the resistance of 
the carborundum crystal varies most rapidly 
with a local potential of 1 to 1.2 volts, under 
which conditions a variation of .01 volt due to 
incoming wireless oscillations will cause a 
variation of about 4 per cent, in the resistance, 
and a consequent variation in the current 
strength appreciable in the telephone receiver 
as sounds. It is less than one-twentieth as sensitive as the magnetic or 
electrolytic detector, and is comparable with steel-carbon detectors. It 
possesses an important advantage for shipboard use in that its 
operation is not disturbed by jarring. The carborundum detector is 
used quite extensively by the American De Forest Company and in 
many amateur stations. 

In experiments made by Mr. H. J. Rounds with carborundum as a 
detector, he found that inductance or capacity in series with the an¬ 
tenna did not improve the signals. Choke coils l l, Fig. 5, each con¬ 
sisting of 150 feet No. 30 wire wound in one layer on a paper tube, 
distinctively improved the signals. Four dry cells b, variable by 
potentiometer p, were employed. With powdered carborundum in a 
glass tube between 2 copper plugs the pressure of which could be 
regulated by a spring, the most favorable results were obtained when 
inductance b c was large and capacity c was email. The sensitive¬ 
ness of this arrangement was comparable to that of the electrolytic 
detector. (See El. World, August 25, 1906.) 

The Hozier-Brown Detector.— This detector is employed in the 
Hozier-Brown Wireless Telegraph system in Great Britain. It con¬ 
sists of a pressed pellet of peroxide of zinc n placed between a blunt 
lead contact l and a plate of platinum z, Fig. 6, connected to the 
aerial and ground respectively, and in shunt with a 
storage battery b and a telephone receiver t, or a siphon 
recorder. In practice the detector is placed directly in 
the aerial circuit. When the siphon recorder is utilized 
a light contact arm is attached to its coil to ring an 
alarm. With an aerial 185 feet high signals have been y " 
recorded by this detector at a distance of 100 miles. *=• 

It is said to be reliable and durable and to require very Fig - ^ 
little attention. The detector acts as a batterv while under the influ- 












220 


WIRELESS TELEGRAPHY. 


ence of incoming oscillations and if connected in opposition to bat¬ 
tery b reduces the current strength in the circuit sufficiently to operate 
a siphon recorder, or to produce loud signals in the telephone re¬ 
ceiver. It is automatic in action, its battery effect ceasing instantly 
with the stopping of the oscillations. In other respects the Hozier- 
Brown Wireless Telegraph system does not differ materially from 
other wireless spark telegraph systems. 

Titanium Oxide Detector. — An oxide of titanium in crystal form if 
connected up in like manner to that of k in Fig. 5 with a sharp point 
presented to a clamp m will serve as a detector. Mr. G. W. Pierce, to 
whom this discovery is due, has noticed that silver-tellurid is also 
quite sensitive as a detector. 

Tantalum and Platinum Wire Detectors. — An arrangement of the 
tantalum detector as devised by Mr. L. H. Walter of London is as 
follows: A sealed in platinum wire dips into mercury contained in a 
bulb. Another sealed in wire has clamped to its lower end a piece of 
tantalum filament, about l en gth, which just touches the 

mercury. The mercury is poured into the bulb through an aperture, 
after which the bulb is exhausted and sealed. When properly con¬ 
structed this detector is said to give satisfactory service, being durable 
and sensitive. This form of the device is not suitable for use on 
shipboard, as it is rendered inoperative by jarring. For shipboard use 
a modification of the foregoing arrangement is used, the platinum 
wire being sealed into a small glass bulb on the end of a small glass 
tube, in which is placed a tantalum wire, one end of which dips into 
a drop of mercury 

H. Gernsback of New York has noticed that a Woolaston wire, as 
the very fine platinum wire employed in the electrolytic detector is 
termed (used by Woolaston in 1801. See Author’s article, “Elec¬ 
tricity: Its History and Progress,” Enc. Americana, 1907), will act as 
a detector if carefully placed on a surface of mercury. Careful ad¬ 
justment is necessary, an adjusting screw of very fine pitch being 
necessary to raise and lower the wire from the mercury; the surface 
of the mercury must also be free of dust. Its action appears to be 
microphonic. To avoid the effect of jarring, the instrument should be 
placed on several layers of felt. 

Thermo-Electric Detectors. — Detectors of this type employ the 
well-known principle of thermo-electric couples, in which heat applied 
or developed at the junction of certain different metals, establishes an 


ii - c* nt+r 


VALVE DETECTORS. 


221 


electromotive force. One type of this detector employed in the Tele- 
funken Wireless Telegraph system may be briefly described as follows: 
A fine platinum wire resting on the edge of a small flat copper cup is 
placed with the copper cup in the receiver oscillation circuit, in the 
manner common to auto detectors. A tiny alcohol flame is placed in 
adjustable proximity to the fine wire, heating it and developing 
e. M. F. at the junction of the couple, and consequently also develop¬ 
ing a minute current in the circuit. Incoming oscillations disturb 
this current and produce variations thereof perceptible in the tele¬ 
phone receiver. The operating parts of the detector are enclosed in a 
substantial brass case, from the outside of which the copper cup may 
be turned to find new spots for adjustment, etc. 

Fleming Oscillation Valve Detector. — It has been known for a 
number of years that the air or gas surrounding an incandescent 
wire, filament or other conductor is ionized or electronized (See page 



Fig. 7.—Elster-Geitel Experiment. 



42), due to electrons or negative particles or ions escaping from the 
incandescent body. Probably the first experiments along this line 
were those of Elster and Geitel in 1882, who placed a metallic fila¬ 
ment or wire f in an exhausted bulb b. Fig. 7, and adjacent to, but 
not touching the wire, a platinum plate p. An electric current from a 
battery b heated the wire to a desired temperature, when it was found 
that the plate became electrified, as shown by a galvanometer, this in¬ 
dicating that the intermediate gas was ionized or rendered electrically 
conducting. It was found that the degree of ionization, or the num¬ 
ber of electrons liberated or projected from a heated or incandescent 
conductor, varied with the nature of the conductor. Thus sodium and 
potassium emit electrons at very low temperatures. Carbon and 
tantalum also rank high in this respect. 


















222 


WIRELESS TELEGRAPHY. 


Mr. J. A. Fleming has produced an electric wave detector based on 
the Elster-Geitel discovery, which he terms an oscillation valve de¬ 
tector. This detector is outlined in Fig. 8, in which a is the aerial, l 
the transformer, c the usual capacity, V a heating battery, b the bulb, 
w the filament, p the platinum plate, t a telephone receiver. 

By experiment Fleming has found that this device acts as a cur¬ 
rent rectifier, permitting only the passage of oscillations of negative 
polarity from the filament to the plate. Hence, incoming oscilla¬ 
tions are rectified at the detector and pass into the telephone circuit 
as a fluctuating train of direct current impulses producing sounds or 
signals in the telephone corresponding to those set up at the trans¬ 
mitter. Fleming has also shown by experiment that a device of the 
Elster-Geitel type has a very high resistance at low e. m. f’s., but that 
with an applied e. m. f. of about 20 volts its increase of conductance 
is marked. (See Fleming’s “Principles of Electric Wave Teleg¬ 
raphy,” 1906, page 402.) At the low average e. m. f’s. obtainable at 
the receiving antenna, of the value of tenths, hundredths or thou¬ 
sandths of a volt, such a device would seemingly be inefficient with¬ 
out an auxiliary e. M. f. A somewhat modified form of this detector 
is described in connection with the Marconi Wireless system, herein. 

Telefunken Gas Detector. — In Fig. 9 is outlined a detector recently 
patented in Germany (No. 193,383), apparently a modification of the 
Elster-Geitel tube arrangement. Therein b is a glass bulb containing 
a gas or metal vapor. The anode t is a metal tube, through which 

passes a wire, the cathode, coat¬ 
ed with an oxide of an alkaloid. 
The wire cathode is heated to 
dull redness by an auxiliary bat¬ 
tery b', when the gas is ionized 
and a current flows between the 
electrodes. Incoming electric 
p IG g waves then set up oscillations in 

the oscillation circuit l c c, which affect the resistance of the gas in 
the bulb, or are rectified therein, depending on the theory of action 
adopted, and are reproduced as sound signals in the telephone re¬ 
ceiver r. c is a variable condenser in the aerial a. ck is a choke coil. 
b is a battery in the telephone circuit. 

Arrangement of Electrolytic Detector. — This detector is described 
elsewhere. (See Index.) A convenient arrangement due to Gerns- 
back for using the bare Woolaston wire is shown in Fig. 10, in which 











ELECTROLYTIC DETECTORS. 


223 


p is the fine platinum wire, c is a carbon cup about *4 inch in diame¬ 
ter and of same depth, for holding the electrolyte, 4 parts water, 1 
part nitric acid, b b' are the usual binding posts. The wire is 
moved into and out of the electrolyte by means of the knob and a 
spiral spring n. In the case of the glass point electrolytic detector, 
mentioned in connection with the Shoemaker detector, and elsewhere 
herein, the handling of the wire is simple, but in the case of the bare 
wire detector the matter of connecting the wire to a suitable holder 
by soldering, clamping, or otherwise, is more difficult, owing to the 
extreme fineness of the wire which leads to breakage, etc. Mr. Gerns- 
back has largely obviated this difficulty in the following manner: 
Across a piece of ordinary tin foil about inch long and % inch 
wide one end of the fine wire (about an inch in length) is laid. A 
part of the foil is folded over the wire as a clamp; the foil again 
folded several times, and finally the foil is rolled between the finger 
and thumb into a compact roll, out of which one end of the wire 
projects. Then after screwing up the tubular 
holder n, Fig. 10, to its limit, the small setscrew s 
is unscrewed to its maximum distance and the tin- 
foil roll is inserted into the cavity of the holder 
m, allowing the wire to project as shown in the 
figure. The foil protects the fine wire from screw 
s. For suggestions as to best manner of adjusting 
the electrolytic detector in actual working see 
Chapter XVII. For long distance working the 
thickness of the platinum wire should not exceed 
.0001 to .0003 inch. Fessenden has used wire as fine as .00006. (See 
page 152.) For distances not exceeding 8 or 10 miles wire .001 to 
.005 inch may be suitably employed. 

Sensitiveness of Detectors.— Using a sensitive silicon detector Pick¬ 
ard has made numerous tests at his laboratory, Amesbury, Mass., by 
means of specially designed apparatus to determine the sensitiveness 
of various detectors, as well as to measure the energy of received 
wireless signals. The method in brief, the circuit connections of 
which are shown in Fig. 11, consists in comparing the intensity of the 
discharge of a small condenser against that of the received signals. 
To the right of switch s is shown an ordinary wireless receiving cir¬ 
cuit, consisting of adjustable tuning inductance L, primary and sec¬ 
ondary coils of oscillation transformer t, capacity c, silicon detector 



:224 


WIRELESS TELEGRAPHY. 



d and telephone receiver r. A substitution circuit including a small 
condenser c', potentiometer p and battery b is shown to the left. In¬ 
ductance L is adjusted to give the maximum response in receiver r. 
With switch s turned to the right the operator hears the dots of arriv¬ 
ing signals in receiver r. Throwing the switch to the left and closing 

key k a single discharge of condenser o' is 
heard in the receiver. The capacity o' is 
made equal to that of the antenna, and as the 
inductance of the antenna as compared with 
l and t may be neglected, the frequency of 
the oscillations due to the discharge of c' 
will be equal to that of the distant station 
p IG IT when the discharge in the condenser c' is 

adjusted to equal the incoming signals, as indicated by the intensity 
of sounds in the telephone. This adjustment is made by throwing 
the switch to the right and left alternately and by varying the poten¬ 
tial in the substitution circuit by means of the potentiometer until 
the desired result is obtained. Then, knowing the capacity of c' and 
the potential to which it is charged, the energy of the received signals 
may be calculated by the formula W (ergs) = cv 2 , where c is ca¬ 
pacity and v is potential in volts. Key k' may he used to obtain a 
single click in the receiver from the distant station, by closing that 
key for a small fraction of a second, the sound of which click is bal¬ 
anced against the condenser discharge as before. 

It was found that at a distance of 90 miles from a high power 
transmitting station (Wellsfleet) the maximum energy of received 
signals was .03 ergs, per dot. With the short antenna employed dur¬ 
ing the tests this was equal to a maximum of about 3 volts on the 
antenna. Other measurements by the same experimenter of received 
signals from less powerful stations at distances of from 50 to 100 
miles, indicate that maximum e. m. f’s. of one volt or less, and mean 
E. M. f’s. of less than .001 volt exist on the antenna; in the case of an 
inductively coupled circuit the mean stepped up e. m. f. in the second¬ 
ary circuit is probably 3 to 5 times that of the antenna. 

A high resistance telephone receiver such as is used in wireless 
telegraphy will give a clearly defined dot from the discharge of a 
condenser, corresponding to one-millionth erg. The electrolytic or 
magnetic detector requires approximately one-thousandth to one-hun¬ 
dredth erg to produce a corresponding signal at a frequency of 500,000 







TESTS OF DETECTORS. 


225 


cycles. This indicates, as noted by Mr. Pickard, that were it not for 
the inefficiency of the telephone at high frequencies it would far excel 
the most sensitive detectors now in use; and, further, the foregoing 
results appear to show that the views held with regard to the super¬ 
sensitiveness of wireless detectors on the .assumption that the received 
energy in wireless telegraphy was far below that used in any previous 
branch of electrical signaling are not borne out by the facts, since it 
is demonstrated that the energy now received at the receiving station, 
even over the longest distances yet covered, is hundreds of times 
greater than that necessary to operate the telephone receiver. 

The arrangement shown in Fig. 11 has also been employed by Mr. 
Pickard to measure the sensitiveness of different types of detectors 
with the following results: 

Electrolytic .00364 to .000400 erg. 

Magnetic .000400 to .000430 erg. 

Silicon .000430 to .000450 erg. 

Carborundum .009000 to .014000 erg. 

These measurements indicate that the silicon detector is practically 
of the same order of sensitiveness as the electrolytic detector. In 
practice the actual difference in the sensitiveness of the carborundum 
detector is not so perceptible in the telephone receiver as would be 
indicated by these tests, the explanation offered being that the human 
ear does not determine sound in direct proportion to its intensity, but 
rather as the ratio of the square roots of the intensity of the sounds. 

In later tests the same experimenter has found that with the peri- 
kon detector any received signal capable of giving an appreciable 
sound in the telephone receiver will measurably deflect the needle of 
a 2,000 ohm d’Arsonval galvanometer in a regular wireless telegraph 
circuit, and subject to the usual minute extraneous disturbances of 
such circuits. On circuits free from such disturbances and employ¬ 
ing a much more sensitive galvanometer it was found possible to 
measure received signals to which the most sensitive receiver is irre¬ 
sponsive. In this Case the galvanometer had a period of 10 seconds, 
hence its action is cumulative, while that of the telephone is prac¬ 
tically instantaneous. Mr. Pickard compares this result to the 
cumulative effect of a photographic plate in detecting the light of 
stars that are invisible to the eye. This cumulative effect of the 
galvanometer, however, cannot be utilized in practice, for the reason 
that if the period of the instrument is diminished the advantage of a 


226 


WIRELESS TELEGRAPHY. 


cumulative action is lost. The information concerning the foregoing 
interesting experiments are mainly drawn from data supplied by Mr. 
Pickard, to whom the author is greatly indebted for the courtesy. 

Hot-Wire Ammeter.— The connections of a hot-wire ammeter are 
shown in theory in Fig. 12. It depends for its operation primarily on 
the expansion of a platinum-silver wire caused by the passage of a 
current or currents through it. The wire is kept taut by a light 
weight s. The expansion and contraction of the wire rotates the 
small drum d and with it the needle n; the scale s being calibrated 
to indicate the current strength. These instruments have practically 
no self-induction. 

The Allstrom Selenium Relay.— This relay combines some of the 
features of the Thomson reflecting galvanometer. A small piece of 
very light iron foil i l / 2 or ^4 inch square is suspended as shown in 
Fig. 12a by 2 platinum wires p, .0001 inch in diameter. A small 
mirror m is cemented to the iron foil. The light from a lamp l falls 
on this mirror and is reflected towards a selenium cell s, in the circuit 




Fig. 12.—Hot Wire Ammeter. Fig. 12a. —Allstrom Selenium Relay. 

of which is a battery b and a sensitive relay r, the latter controlling a 
call bell b. A magnet m wound to 10,000 ohms has its pole placed 
directly behind the iron foil and almost touches it. The selenium 
cell is enclosed in a box n , in the front of which is a narrow slot. 
Normally the beam of light does not fall on the slot, but it does so 
when the iron foil carrying the mirror is deflected. Very light oscil¬ 
lation currents, however, traversing the coil of magnet m deflects the 
foil, causing the light to fall on the selenium, reducing its resistance 
and thereby operating the relay r and the call bell. Iron the thick¬ 
ness of the diaphragm of a telephone receiver may be used for this 
device. It is stated that the Allstrom relay will respond to the one- 

















TRANSFORMERS. 


22T 


billionth of an ampere. Its action, however, might perhaps be ex¬ 
pected to be rather sluggish. 

The Sullivan Relay.— This relay is used to a considerable extent in 
wireless telegraphy. Briefly it consists of a small coil of fine wire 
carrying a light aluminum arm with a platinum contact. The coil is 
suspended between 2 powerful magnets, somewhat on the principle of 
the Thomson siphon recorder or the d’Arsonval galvanometer. It will 
record signals through 250,000 ohms with 1 dry cell and will respond 
as a call bell or alarm relay with 1 cell through 5,000,000 ohms. 


Transformers.— It is known that with open transmitter circuits 

(page 53) of a given capacity a desired increase of the energy stored 
up in the aerial to effect long distance transmission of signals is ob¬ 
tainable by increasing the potential at the transmitter. This usually 
involves an increase in the length of the spark gap which results in a 
more rapid damping of the oscillations, due to the increased resist¬ 
ance of the spark gap. (See page 203.) Experience has shown that 
the increased damping of the oscillations due to this cause generally 
more than offsets the advantages of the increased potential where res¬ 
onance or sustained radiation is desired. For this and other reasons 
recourse was had to the use of closed transmitting circuits (page 49), 
in which more persistent oscillations are established by the discharge 
of a capacity c c, which oscillations are impressed on the aerial by an 
oscillation transformer t. Further, to obtain increased capacity in 
the aerials for the storage of electrical energy for radiation, the num¬ 
ber of vertical wires has been increased and these, as previously noted, 
have been extended aloft in the t l, “harp,” “umbrella” and other 
forms. By these means an increased amount of wave energy is radi¬ 
ated with a given potential at the spark gap. 

In numerous wdreless stations also, in order to obtain a larger 
initial output of energy, power transformers have displaced induction 
coils with their hammer or other types of interrupters. For the 
general improvement of the service also recourse has been had to more 
accurate means of tuning in wireless transmitter and receiver cir¬ 
cuits. To better effect this object in transmitter circuits resonance is 
in some cases utilized between the primary and secondary circuits of 
power transformers. For these transformers the primary current is 
usually supplied by a 60 cycle alternating current generator at 110 
volts. 



228 


WIRELESS TELEGRAPHY. 


The types of transformers employed are the open core, or induc¬ 
tion coil, form (See page 203), or the closed core type. The closed 
core type is the more economical in that having a completed mag¬ 
netic circuit in the core it only requires for a given output about one- 
fourth of the number of turns of wire in the primary and secondary 
coils as are required in the open core transformer, but, excepting some 
very high power stations, the open core transformer is the more gen¬ 
erally employed, for reasons of practical efficiency. 

In testing separately the voltage and current of a transformer cir¬ 
cuit it is usually found that the product of these quantities, in other 
words, the power in watts of the circuit, is greater than the indica¬ 
tions given by a watt meter, due to the fact that the currents in the 
primary and secondary circuits are not in phase. If, for instance, the 
product of the volts and amperes of a transformer circuit is 500 and 
the watt meter indicates 250 watts, the ratio of the first to the sec¬ 
ond is 500 : 250 = .5, that is one-half of unity. This ratio is termed 
the power factor of the machine. The output of a transformer is ordi¬ 
narily given in kilowatts at 100 per cent, power factor. In the in¬ 
stance given the power factor would be 50 per cent, of unity, and in 
reality its effective output would be one-half of the rated output. 
Certain tests in practice have shown that the pow r er factor increases 
up to a certain point with an increase in the length of the spark gap 
in wireless telegraphy, but beyond a certain critical point the damping 
effect increases very rapidly. 

With a current of 60 cycles per second in the primary circuit of a 
transformer there will be 120 alternations of current per second, and 
if the secondary coil and the length of the spark gap are so chosen 
that the length of the gap breaks down just at the maximum e. m. f. 
of each alternation in the secondary circuit, there will be 120 spark 
discharges per second in the oscillation circuit; and 120 trains of 
waves, each lasting for a comparatively short time, will be radiated 
from the antenna. If, however, the potential of the secondary is such 
that before it reaches its maximum e. m. f. the gap breaks down, there 
will be a tendency to the formation of an arc at the gap, which may 
continue while the e. m. f. of the alternation is rising to its maxi¬ 
mum and until it falls to a point too low to maintain the arc, at which 
time an oscillation discharge may take place, but owing to the low 
potential of the discharge at that instant the energy of the radiated 
waves may not be far-reaching. Further, the heating at the gap is 


TRANSFORMERS. 


229 


much augmented by undue arcing, this adding largely to heat losses. 
Again, in closed core transformers more especially, the mutual in¬ 
ductance between the coils, if not compensated in some manner, tends 
to maintain the potential across the terminals of the secondary coil at 
the moment of break down of the air gap, at which instant the circuit 
is virtually short circuited at the gap, and the strong current thereby 
maintained may also sustain an arc. This action may be diminished 
or obviated by a series inductance in the primary or in the secondary 
circuit whereby the capacity and inductance reactances of the circuit 
are balanced or offset, with the result that resonance is obtained be¬ 
tween the primary and secondary circuits. To obtain this balance the 
inductance reactance (271?il) must equal or balance the capacity 
reactance (2 nnG) where 2 n is 6.28, n is the frequency, l is the 
inductance and c is the capacity. When this balance is found there 
will be practically no impedance in the circuit and consequently no 
lagging currents. (For an elementary treatment of inductance and 
capacity reactances, impedance, etc., the reader may be referred to the 
Author’s “American Telegraphy,” page 100.) 

The use of inductance in the primary circuit has been found to 
permit a considerable reduction in the amount of turns necessary in 
the secondary coil of the closed transformer. In the case of certain 
open core transformers (See Fig. 13) designed to give resonance in 
wireless telegraphy, the secondary coil is wound with the largest wire 
practicable, to reduce resistance. The generator contains a certain 
amount of inductance in its armature and an inductance is sometimes 
inserted in the primary circuit, by means of which “loose coupling” 
between the generator and primary coil is obtained. Finally, in 
actual practice the primary and secondary circuits of the transformer 
may then be brought into resonance by proper adjustment of the po¬ 
tential and frequency of the generator, the inductance or turns of the 
primary coil, of the capacity load in the secondary circuit and of the 
length of the spark gap. 

An open core or induction coil type of a 5-kilowatt transformer 
employed in the Telefunken wireless service is illustrated in Fig. 13. 
s s are terminals of the secondary coil, p p are the terminals of the 
primary coil. The external dimensions of this transformer are prac¬ 
tically equal to the induction coil described elsewhere (See page 202). 

By means of resonance between the primary and secondary circuits 
of the transformer it is found practicable to separate the spark gap 


230 


WIRELESS TELEGRAPHY. 


to a point at which several alternations or swings of the current are 
necessary to charge the secondary circuit to the sparking potential. 
For instance, in the case of a 60 cycle current the sparking distance 
might be arranged to allow 60 or 30 sparks to pass per second. The 
result of this arrangement is that while there are fewer discharges 
of the condenser per second a higher potential is attained at each dis¬ 
charge and correspondingly further signaling distances may thus be 
covered with a given expenditure of energy. It has been suggested 
that this method of accumulating the energy of several successive 
swings in the secondary circuit might be utilized to advantage in 
calling stations by employing a very low spark discharge, whilst a 
higher rate could be availed of for sending messages. There is a limit 
to the permissible reduction of spark discharges per second in the 
secondary circuit, owing to the fact that when the discharges fall 



Fig. 13.—5-Kilowatt Open Cove Transformer. 


somewhat below 30 per second the arriving oscillations become in¬ 
audible in the telephone. Again, experience has shown that the ear 
is more acute to high tones than low tones, and for this reason alone 
a range of about 60 discharges per second is preferable in practice. 
It is further found that atmospheric discharges down the antenna give 
a low tone in the receiver which would tend to confuse signals from 
a slow discharge spark gap. Atmospheric discharges due to electric 
potential in the atmosphere will, it is known, pass to earth down any 
aerial conductor, experiments with which have often been made with 
aerial wire upheld by kites, etc. In wireless telegraph parlance these 
discharges are termed x’s. They at times produce noises in the tele- 


COUPLING. 


231 


phone receiver that are heard 6 feet away from that instrument. As 
noted elsewhere, counterpoises in place of direct earth terminals are 
efficient in eliminating x ? s. 

When the primary and secondary circuits of the transformer are in 
resonance the voltmeter in the primary circuit gives a practically 
uniform reading during the continuance of regular alternations in the 
primary circuit. Other things remaining the same, the number of 
w r ave trains transmitted per second may be increased by increasing 
the e. m. f. of the generator, since this produces more frequent dis¬ 
charges at the spark gap. In actual practice, with an open core res¬ 
onance transformer similar to that shown in Fig. 13, the normal 
e. M. f. of the generator being 110 volts, 60 cycles, it is found pos¬ 
sible by increasing the generator e. m. f. to 200 volts, by removing 
inductance from the primary of the transformer circuit, by increasing 
the length of the spark gap to 2.75 inches and by ventilating the 
spark gap to accelerate damping, to obtain a much increased number 
of highly damped wave trains, about 300 per second, of large ampli¬ 
tude (explosive discharges), with a total capacity load of .002 micro¬ 
farad in the oscillation circuit from 3 small jars (4 inch diameter) 
arranged with 3 in multiple in series of 3, without developing an arc 
in the spark gap and without injury to the Leyden jars. Signaling 
distances of 1,200 miles over sea have been reached by this arrange¬ 
ment with an l aerial 180 feet high. 

In general it may be noted that with a given transformer output, 
and within certain limits, greater distances will be covered by utiliz¬ 
ing the natural wave length of the transmitting aerial wire and tun¬ 
ing the receiving station therefor than by adjusting the aerial down 
or up to an arbitrary oscillation period. 

Tight and Loose Coupling.— More accurate tuning and improved 
resonance are now also available by the use of loose coupling, as it is 
termed, of the aerial circuit to the transmitting and receiving oscil¬ 
lation circuits, respectively, which methods are now quite generally 
adopted. Some ingenious methods and apparatus to facilitate and 
simplify the adjustment of loose and tight coupling have been de¬ 
scribed elsewhere. (See Telefunken system.) Others will presently 
be described. 

By tight and loose coupling is meant respectively the more or less 
direct connection or inductive relation of the aerial circuit to the 
transmitting and receiving oscillation circuits. Instances of loose and 


2 32 


WIRELESS TELEGRAPHY. 


tight coupling are shown on pages 49, 1G2. In Fig. 24, page 49, loose 
coupling is made by means of an oscillation transformer with primary 
and secondary coils. In Fig. 98a- (Shoemaker system), the coupling 
is made by an auto-transformer. These methods of coupling are also 
termed respectively indirect (or inductive) and direct coupling. In 
loose coupling in which an oscillation transformer is employed the 
further the coils are separated the looser is the coupling. Loose in¬ 
direct coupling is advantageous in that it largely reduces mutual in¬ 
ductance reactance, and consequently reduces damping of the oscilla¬ 
tions. Such coupling reduces the strength or intensity of the received 
signals, but adds to their clearness. Again, while loose coupling gives 
sharp tuning and persistent oscillations, the amplitude of the waves 
is diminished thereby. According to Eichhorn, in certain conditions of 
loose coupling the oscillations per discharge (Consult Eichhorn’s book 
“Wireless Telegraphy/’ page 35) are increased 3 fold, while the ampli¬ 
tude of potential is diminished 47 fold. Abrahams has shown that 
maximum potential at the top of the aerial is less desirable in com- 
paratively close coupled circuits than a loop of current at the lower 
end t hereo f. Wein notes that this current loop is nearly proportional 
to Vcc, in which c is the capacity of condenser oscillation circuit 
and o' that of the aerial, hence an advantage of a number of aerial 
wires. For loose coupled circuits these considerations do not apply so 
materially, as persistent oscillations rather than intensity are then de¬ 
sired. In general for loose coupling or to obtain persistent or sus¬ 
tained oscillations many parallel aerial wires are not so essential as 
for close coupling, as wires in parallel reduce the inductance which is 
desirable in this case. For close coupling, however, and so-called ex¬ 
plosive radiation, which is usually accompanied with non-persistent, 
or highly damped, oscillations, multiple aerials are advisable. Meas¬ 
urements with the wavemeter indicate that in syntonized coupled os¬ 
cillation circuits there are usually two sets of oscillations of different 
frequencies, both different from the normal or natural frequency of 
the respective circuits. The wave lengths of the respective oscilla¬ 
tions may be ascertained by noting the readings of a wavemeter, from 
which a curve may also be plotted showing the relative amplitudes of 
the respective oscillations by observing the magnitude of the current 
strength of each oscillation in turn, as indicated by the height to 
which the liquid rises in, for instance, the Donitz wavemeter, or by 
the degree of luminosity in the tube or bulbs of the Fleming and 



COUPLED CIRCUITS. 


233 


other wavemeters (see Index) ; or by the lowness of the tone or sounds 
in the telephone when a sensitive detector is used for this purpose. 
Further, the degree of sharpness of the tuning may be deduced by 
noting whether the maximum indications of the w T avemeter decrease 
rapidly or slowly, as the oscillation circuit undergoes small variations 
of adjustment, towards either side from the position of resonance. 
If rapidly, a low decrement of damping or persistent oscillations are 
indicated; if slowly, a high decrement of damping. These results 
w r ould be indicated on the plotted curves by a pointed or a round peak, 
respectively. In practice these curves are termed the upper and lower 
“humps.” Thus in a recent test in practice, the fundamental wave 
length of the aerial being 335 meters, direct coupled to the oscilla¬ 
tion circuit, the w f ave lengths employed were found to be 420 meters 
for the upper hump and 318 meters for the lower hump. In receiv¬ 
ing wureless signals under these conditions the circuits must be tuned 
for one or other of the two sets of oscillations, and obviously there is 
a loss of energy. To utilize the energy of both sets of oscillations 
Fleming has recently suggested the employment of 2 receiving circuits 
tuned respectively to one set of oscillations and in connection wkh 
these tuned circuits a telephone receiver with 2 coils, one in each re¬ 
ceiving circuit. 

The foregoing phenomenon of inductively coupled circuits is thought 
to be analogous to the following action of two swinging weights 
on a horizontal string. In performing this well-known and simple 
experiment several years ago the writer stretched a piece of cord be¬ 
tween the envelope slots in his desk and used as weights two iron nuts 
about Yz inch square suspended from the horizontal string by pieces 
of string 6 inches in length. When one of the weights (a) is set 
swinging it imparts motion via the horizontal cord to the second 
weight (b). This work of driving the weight (b) soon brings the 
weight (a.) to a standstill, at which time weight (b) is at its maxi¬ 
mum swing. Weight (b) now becomes the driver and presently 
weight (a) is in full motion, whilst weight (b) comes to a halt, and 
these operations are repeated many times before the initial energy is 
expended. The writer also experimented with a number of weights 
with different lengths of vertical string and at different distances 
apart on the horizontal string, with many interesting and it may be 
said amusing results in sudden cessation, starting, etc., of the weights. 
The horizontal string should not be too taut. Analogously it is as- 


234 


WIRELESS TELEGRAPHY. 


sumed that the high frequency oscillations of the primary circuit set 
up oscillations in the aerial circuit which in turn react on the pri¬ 
mary, and thus two sets of oscillations are established. As Fleming 
has pointed out, when either circuit acts as driver its rate of oscilla¬ 
tions are diminished, while those of the driven circuit are increased, 
which, according to this analogy, would account for the higher and 
lower frequency oscillations in these circuits. (See Figs. 15, 16, 
Telefunken Singing Spark.) The writer at the time of making these 
said experiments sought to find an analogy between the actions noted 
and that of the primary and aerial oscillation circuits of a wireless 
system, but in the absence of knowledge relative to the existence of 
two different oscillations in the coupling circuits (which the wave- 
meter has subsequently revealed) concluded that such reciprocal ac¬ 
tions of the circuits would nullify radiation. 

Experience has shown that the oscillation of lower frequency 
(longer wave length) has the lowest decrement of damping; that is, 
its train persists longer than the train of higher frequency. In tests 
by Ferdinand Braun in connection with his directed wave experi¬ 
ments it was found that of the two oscillations always found in each 
transmitting wire the stronger of the two oscillations had the shorter 
wave length. The looser the coupling between the aerial and the 
closed oscillation or condenser circuits the less will be the difference 
between the two oscillations or humps, and contrariwise. In direct 
coupled circuits this difference is proportional to ^/c f -~ c, where c is 
the capacity of the condenser oscillation circuit and c' that of the 
aerial circuit. 

Sliding Contact Tuning Coils.— A common form of tuning coil at 
one time in very general use and which is still employed quite ex¬ 
tensively in wireless installations is indicated in Figs. 14, 14 a. The 
tuning coil t is arranged in a spiral of No. 16 or No. 18 insulated 
copper wire wound on a suitable drum and enclosed in a case, as 
shown. A vertical opening or slot is made on one side of the case, 
and opposite this opening the insulation is removed from the spiral. 
Three sliding contacts bed are movable up and down on guides g 
on the side of the case. Fingers on these sliding contacts, indicated 
by the arrows in Fig. 14 a, make connection with one part or another 
of the spiral wire, thereby including more or less of the coil in ex¬ 
ternal circuits. Flexible wires are attached to the sliding contacts, 
b and c, leading to the detector; d leads to earth and a to the aerial. 


VARIOMETERS. 


235 

The exact arrangement of these connections may of course vary in 
different apparatus. The wave lengths that correspond approximately 
to the position of the slides are sometimes indicated on a scale on the 
side of the case. Adjustment is made by moving the contacts up or 
down on the coil until signals are re¬ 
ceived, but the obtainment of best sig- 
nals promptly is largely a matter of ex¬ 
periment and skillful adjustment of the 
contacts on the part of the operator. 

The use of sliding contact tuning 
coils with their accompanying disad¬ 
vantages, due to imperfect contacts, etc., 
is giving way in many of the larger 
wireless stations to continuously varia¬ 
ble inductances, variometers, etc., de¬ 
scribed elsewhere. It is not uncommon 
in practice to find the strength of sig- Figs. 14 , 14 a. 
nals reduced 50 per cent, by the introduction of resistance at the slid¬ 
ing contacts. In long distance signaling considerable difficulty has 
been met with in getting accurate tuning owing to the tendency of the 
slider to rest on two coils at once. In some systems this has led to 
the adoption of plug inductances in which the coils are arranged to 
vary the tuning in very small steps. (See Marconi system.) 

Variometers, Variable Oscillation Transformers and Condensers.— 
The variometer makes possible a continuous variation of the fre¬ 
quency of the receiving circuits in which it is placed in contradistinc¬ 
tion to step by step or sliding contact tuning coils. Instances of 
continuously variable tuning coils including the variometer are given 
in connection with the Telefunken system, Chapter IX. The vari¬ 
ometer employs the principle of the well-known Ayrton and Perry 
standard of induction. There are a number of different mechanical 
arrangements of this device now in use, amongst others the Lorenz 
variometer, illustrated in Fig. 15, which consists of two coils, the 
outerhme fixed, the inner coil movable by the knob k. The coils are 
connected in series either in the aerial circuit or in the closed oscilla¬ 
tion circuit of the receiver, by means of the screw posts s s. When 
at right angles to one another the coils give their minimum in¬ 
ductance and the maximum when they lie in the same place. Jn 
practice sometimes three of these variometers of different capacities 



































2 30 


WIRELESS TELEGRAPHY. 


) 


are placed in series in a circuit to produce an increased amount of in¬ 
ductance; the first in the series, for instance, having a range of from 
.33 to 3.3 microhenrys, the second a range from 3 to 30 microhenrys, 
the third from 29 to 290 microhenrys. When the coils of a variometer 
are tuned to the point of minimum inductance, or zero point, they 
are automatically short circuited, thereby preventing loss of energy 
due to the resistance of the coils. The conductors of these coils are 
stranded and are so wound that an equal amount of each strand lies 
on the outside of the cable, thus minimizing skin resistance for high 



Fig. 15. Fig. 15a. Fig. 15b. 


frequency currents. An inductive coupling device or receiver oscilla¬ 
tion transformer is shown in Fig. 15a. In this the inner coil is fixed; 
the outer coil may be rotated by the knob k. Either coil may be 
used as the primary or secondary coil of a wireless system. Fig. 155 
represents a type of variable air or oil condenser for the receiver cir¬ 
cuit, consisting of two series of semicircular aluminum plates, one 
series being fixed, the other movable by the knob k, to or from prox¬ 
imity with the fixed plates, p is a pointer that moves over a gradu¬ 
ated scale (see Condenser, Variable, Index), thereby indicating the 
capacity of the condenser with the plates in a given position. The 
range of this condenser is from .00005 to .005 microfard. In prac¬ 
tice it is enclosed in a case. 








CHAPTER XV. 


DIRECTIVE WIRELESS RADIATION. 

STONE LOCALIZER OF ELECTRIC WAVES-DE FOREST AEROPHORE-DE 

FOREST BENT ANTENNA-MARCONI BENT ANTENNA-BRAUN DI¬ 
RECTIVE WIRELESS EXPERIMENTS-ARTOM, BELLINI AND TOSI DI¬ 

RECTIVE, WIRELESS SIGNALS. 

As previously noted, the attempt to concentrate and reflect electric 
waves (as light, for instance, is concentrated), by means of metallic 
mirrors, was not successful, owing to the difficulty in meeting the re¬ 
quirement that the mirror must be large in comparison with the elec¬ 
tric wave. (Page 25.) This difficulty is obvious when the great 
length of the waves now used in wireless telegraphy and telephony is 
considered, for instance, with a frequency of 100,000, over 9,840 feet. 
On the other hand, the length of the ether waves constituting light is 
so infinitesimal that the smallest mirrors that can be made, or even 
floating particles in air, are large by comparison with electric waves. 
(See page 34.) 

Some success has been achieved recently in the matter of directive 
wireless signaling by methods different from the reflection or mirror 
method, a description of which will presently be given. 

Wave undulations or vibrations of simple harmonic form are usu¬ 
ally shown graphically as a sinusoidal curve or sine wave, derived, for 
instance, from the motion of a point on the circumference of a rolling 
wheel, or from the tracing made by the movement of a pencil point in 
a rectangular slot, under which a strip of paper is drawn with a uni¬ 
form motion; the oscillatory movement of the pencil corresponding 
to a point moving back and forth along the diameter of a circle. In 
Fig. 1 the vertical lines l m n may represent such a back and forth 
motion, the line A b the forward motion of the wheel or wave, and x 
x ' the distance covered by one revolution of the wheel; this corre¬ 
sponding to a wave length. If the vertical lines indicate the to and 


238 


WIRELESS TELEGRAPH* 


fro motions of particles of the medium in which waves are occurring, 
the length of a vertical line between the zero line a b and the point of 
intersection of the curve will represent the extent of motion of a given 
particle or of the wave at a given point and instant. This is graph¬ 
ically shown by the horizontal lines from vertical line c c' in the 
circle to b a; a' b' on the curve. When used to represent an alternat¬ 



ing current wave these lines indicate the strength of current or the 
E. M. F. at any given point and instant of the cycle. 

The period of a wave is the time taken by a particle to move from, 
say, point x around the circle to point x again; or for the pencil point 
in the slot to perform a to and fro motion. On the solid horizontal 
line this, as previously intimated, would correspond to the distance 
x x'. In wave motion it is understood that the particles of the 
medium do not move forward with the wave, but merely rise and fall 
like chips on the surface of a pond as the waves pass under them. As 
the w r ave progresses each particle of the medium in turn rises to the 
crest and falls to the trough of the wave. In an elastic medium it is 
assumed that the particle is displaced from its zero position by a 
force or strain which it resists with a counter force termed stress, 
the stress varying with the extent of the displacement, and tending to 
restore the particle to zero position. 

The position of a point or particle at a given instant relative to 
any fixed position is termed the phase, and the difference of position 
of a given point or particle relative to another particle during its mo¬ 
tion over a circle is termed phase difference. Thus a particle at b 
will pass through point c before particle a, the direction of motion 
being as shown by the arrow, and their phase difference when measured 

























STONE LOCALIZER. 


239 


as an angle will be equal to the difference of the angles made by their 
radii with a fixed line a x. For instance, the difference of phase be¬ 
tween a particle at c and one at x is 90°, or one-quarter wave length, 
while a particle at c and one at c' will have a phase difference of 
180°, or half a wave length. When two particles pass through the 
same point at the same time they have no phase difference. Any two 
particles one wave length apart are said to be in the same phase, and 
two waves of the same frequency whose corresponding parts are mov¬ 
ing in opposite directions with the same velocity are said to have a 
phase difference of 180°. 

For present purposes the curved line in Fig. 1 may be considered 
to represent the contour of an electric wave, in which case that por¬ 
tion of the curve above the line x x' may represent an electric posi¬ 
tive force or sign, that below the line a negative force or sign, and 
the magnitude of the force of the wave at a given point and instant 
may be represented by the length of the vertical lines betwen x x' 
and their intersection with the curve. In this view waves of different 
or equal phase and magnitude and agreeing or opposing in direction 
or sign may be caused to, more or less, assist or neutralize one other, 
instances of which actions will be mentioned in the course of this 
section, and analogous instances of which may be found in text-books 
on light and sound. 

The Stone Localizer of Electric Waves.— In 1902 Mr. John Stone 
Stone patented a device for determini/ig the direction of space 
telegraph signals, which if not a prototype of some of the devices 
employed in more recent experiments in directive wireless signaling, 
may perhaps be regarded as suggestive thereof. (See U. S. Patent, 
No. 716,135, 1902.) 

In Fig. 2 is outlined the theory of this device, v v' are vertical 
wires placed on a common axis a, and in series with which are coils 
x y, respectively. These coils may be so wound, as indicated in the 
figure, that when oscillations of equal strength and direction simul¬ 
taneously pass through them from wires v v', the coil z, which is in 
equal inductive relation to those coils, will not be affected. In the 
circuit of coil z are placed a detector d, condenser c and telephone t. 
When, however, the oscillations in coils x y are in opposite directions 
or differ in strength, z will be affected. In order to obtain the max¬ 
imum effects of the wave energy the wires v v' in the Stone arrange- 


240 


WIRELESS TELEGRAPHY. 


ment are placed the distance of half a wave length apart. Assum¬ 
ing the length of arriving waves to be 50 feet, that the wires are 25 
feet apart and that their plane is in the line of motion of an ad¬ 
vancing wave, the wires w T ill receive the waves at a phase difference of 

180° ; half a wave length. Conse¬ 
quently the oscillations due thereto 
will be of equal strength, for in¬ 
stance, 10, in the figure, but op¬ 
posite in sign, or direction, in the 
coils x y, and therefore coil z will 
be inductively affected in this case 
to the maximum extent. If the 
wires are moved so that the distance 
between them is less than a half 
length the sign in the respective 
wires may still be opposite, but the strength in each will not be equal. 
If, for example, wire v' is moved to the point indicated by dotted line 
n, the force of the wave at v will still be 10+, while at v' it will be 
less than 10—, hence the oscillation current strength in coil x will 
predominate over that in coil y and coil z and detector d will be 
energized. Or, again, keeping the wires half a w T ave length apart, but 
rotating them on the axis a until their plane is perpendicular to the 
front of an advancing wave having at a given instant a force of, say, 
IL0 —j—, it v/ill fall on both wires as indicated by the horizontal line m, 
in a position where the force and sign are equal. Oscillations of equal 
strength and direction will then be set up in the vertical wires and 
coils x y, the effect of which on the coil z will be nil, for reasons 
stated. To determine then the direction of arriving waves it is only 
necessary to move the wires v v' on their axis a until the combined 
forces of the oscillations in the coils x y upon z are nil, which in this 
case will be when the plane of the wires is at right angles to the direc¬ 
tion of the arriving electric waves. 

Obviously on shipboard there is no occasion to rotate the vertical 
w r ires, since the position of the ship may be readily changed 

to effect the same results. Tests were made with this device 
several years ago on the IT. S. Collier Lebanon that determined 
the bearings and cross-bearings from wireless telegraph stations at a 
distance of about 30 miles with a precision of about one-half a point. 
Subsequently tests were made between the battleships Washington 


fit tlTT' 
i 'V > 



Fig. 2.—Stone Localizer. 







AEROPHORE. 


241 


and Tennesee in mid-ocean, in which the bearing of the Washington 
from the Tennessee was determined at a distance of 75 miles with a 
precision of about two-thirds of a point. According to Mr. Stone, 
the apparatus has never been used with a wave length exactly twice 
the distance between the two aerials, and the only object in having the 
wave length equal to twice the said distance is that this arrangement 
of the wires gives maximum intensity of signals; the signals under 
all conditions being the maximum when the plane of the waves is at 
right angles to a plane down through the two antennae; the signals 
being absolutely zero always when the plane of the waves is parallel 
with the plane passing through the two antennae. 

De Forest Aerophore and Bent Antenna. — In the course of his 
practical experience De Forest noticed that certain stations received 
signals to better advantage from one direction than from others, and 
on investigation this was ascertained to depend on the direction in 
which the aerials were disposed relative to the distant station. For 
example, using a grid of vertical wires in one plane, De Forest found 
that the transmission and reception of signals were best from a direc¬ 
tion perpendicular to the plane of said wires. Hence by turning 
the grid to face a desired station it was possible to obtain a measure of 
directive effect, which it was thought might be available on light¬ 
houses and ships to determine their respective vicinities. To facili¬ 
tate this object De Forest constructs apparatus termed the aerophore, 
consisting of a grid of vertical wires operated by a train of gearing, 
whereby the grid may be mechanically rotated to face in any desired 
direction, back and forth. At the same time certain code signals 
are automatically transmitted. These signals indicate the direction in 
which the signals are propagated; east, north, west, south, etc. Hence 
a vessel equipped with an aerophore on receiving these code signals 
can determine the direction from which they have emanated and be 
governed accordingly. 

De Forest also discovered that by using a vertical wire, to which is 
attached a pivoted horizontal wire, with the usual detector in the 
vertical wire, signals are received, the strength of which “vary accord¬ 
ing as the position of the wires approach or depart from a position 
of parallelism with the direction of travel of the waves.” (See U. S. 
Patent, No. 771,819, 1904.) It may be noted that the various 
arrangements of t and l antennae now so largely employed for ca¬ 
pacity on shipboard and land stations correspond more or less to the 


WIRELESS TELEGRAPHY. 


94 9 
A. A 

foregoing device. The practical experience thus far gained does not 
appear definitely to indicate that in ordinary shipboard working the 
signals are affected favorably or unfavorably as regards the directive 
effect on signaling by this arrangement of the antenna. 

Marconi Bent Antennae. — Marconi has made numerous experiments 
relative to directive wireless signaling and has found that by placing 
a large number of wires arranged as an l aerial, or, as it is termed, 
bent antenna, and with the open end pointing away from the distant 
station, the direction of effective radiation or transmission may be 
largely controlled. Also that by using a similar antennae the recep¬ 
tion of signals is largely improved. This arrangement of antennae is 
now employed in a number of the Marconi high power stations with, 
it is reported, marked success. The highest of the vertical wires at 
these stations is 210 feet. The length of the horizontal wires is 2,500 
feet. The total amount of wire in the aerial is about 35 miles, which 
would imply the employment of about 60 vertical and 60 horizontal 
wires, which are upheld by numerous masts. 

This bent antenna arrangement is also used to advantage on a 
smaller scale in the Marconi portable outfits for military purposes. 
In this case the mast employed is about 30 feet high. The horizontal 
wire is about 400 feet long and is pivoted at the top of the mast. In 
practice a man carries the far end of the wire in a circle around the 
mast until the operator announces the best position for signaling. 

Braun Directive Signaling Experiments. — Braun was perhaps 
amongst the first to attack the problem of directive wireless signaling 
in a manner apart from the use of metallic mirrors, although in his 
first experiments he employed an equivalent thereto, using an arrange¬ 
ment described in his German patent of July 13, 1901, in which he 
shows a number of vertical transmitting wires arranged in a parabola. 
Assuming the oscillations in these wires to commence simultaneously, 
a wave will be produced in a plane at right angles to the axis of the 
parabola and will proceed in the direction of the axis; but, as in the 
case of a metallic mirror, the large dimensions of the parabola in this 
arrangement would render it impracticable. 

Dr. Braun subsequently conceived the idea, however, that a simple 
system of transmitting aerials might be constructed that could be 
made to interfere with a wave in one direction and intensify it in 
another. For this purpose he devised a plan consisting of 3 vertical 
wires that may be designated as a, 1, c, on poles erected at the corners 


artom’s experiments. 


243 


of a right angle triangle, in the center of which is an operating room 
into which horizontal wires are led from the foot of the vertical wires. 
By suitable apparatus within the building synchronous oscillations 
are set up in wires a and b , while oscillations of the same frequency, 
but lagging slightly behind or slightly leading the oscillations in wires 
a and b, are set up in wire c. If the oscillations in wire c are lag¬ 
ging, interference between the oscillations of a and b ensues and an 
electrical shadow is thrown from the direction of c and between a and 
b. Contrariwise, if the oscillations in wire c slightly lead those of 
a and b, a wave of greater intensity is projected in the direction men¬ 
tioned, while a shadow results back of wire c, and interference takes 
place at the sides of a and b. By means of a suitable switch in the 
operating room it is feasible to transmit messages in 6 different direc¬ 
tions by interchanging the office of wire c with that of a and b. In 
these experiments the poles were 65 feet high, the sides of the triangle 
98 feet. The aerial wires were 108 feet long and terminated in wire 
nettings. Variable capacities and inductances were employed for the 
adjustment of the frequencies of the system. The distance transmit¬ 
ted in these experiments was about 4,260 feet. The results of the 
experiments showed that the waves could be directed in a fairly definite 
direction, but no practical use has been made of the method. A full 
description by Dr. Braun of this arrangement is translated in the 
London Electrician, 1906. 

Artom’s Experiments in Directive Wireless Telegraph Signaling.— 

Text-books on optics explain that white light is composed of waves of 
varying length pointing in every direction. In this condition the 
waves are said to be non-polarized. When light waves are by any 
suitable means placed parallel with each other the waves are then said 
to be plane polarized. When, on the other hand, any two waves having 
equal amplitude and a difference of phase of one-quarter wave length 
are set at right angles to one another, rotating polarization is pro¬ 
duced. If the difference of phase is greater than one-quarter wave 
length the waves are said to be elliptically polarized. 

Acting on Righi’s analytical demonstration that a combination of 
two electric oscillations rectangular to each other and having equal 
intensity, equal frequency and a phase difference of one-quarter wave 
length, will lead to the production of oscillations with rotating polari¬ 
zation, and polarized waves in a certain direction, Count Artom has 
endeavored to obtain directed waves in wireless telegraphy. 

To attain this object Artom conducted numerous experiments, but 


244 


WIRELESS TELEGRAPHY. 


has obtained his more satisfactory results with the following arrange* 
ment. He places two wires w w', Fig. 3, at right angles to each other, 
somewhat like two rods of a tripod. At the lower end of w he con¬ 
nects a coil a placed within a Leyden jar. At the lower end of w' 
is attached a coil a', the secondary of another coil c. The jar and 
coil c have compensating capacities n n' attached to them. The wires 
are charged indirectly by the transformer t and the Tesla coil t, with 
spark gaps s s'. 

By this arrangement the wire w f is charged by electromagnetic in¬ 
duction while wire w is excited by electrostatic induction. Wires 
w w ' are insulated from one another, and thus constitute two open 
circuit oscillators, in which oscillations of equal amplitude, and a 
phase difference somewhat greater than a quarter wave length, are set 
up. For the receiving apparatus two rods similarly arranged are 
placed at a distance of 18 feet from the transmitter and 9 feet from 
the wall in a room 36 feet long. The wave length chosen was 36 feet. 
A Braun tube excited by a Wimshurst machine is used as an indicator 



Fig. 3- Fig. 4. Fig. 5. 


of the pressure of electric oscillations, being placed across the upper 
terminals of the receiving rods. The small electric wave image of the 
electric waves is observed as a curved shadow around the fixed lumin¬ 
ous spot of the Braun tube. Artom points out that the existence of 
elliptically polarized waves is proven by the fact that if the receiver is 
moved towards the center of the room the shadow disappears. 

In carrying out his more practical experiments Count Artom em¬ 
ployed a number of different arrangements of aerials, in general con¬ 
sisting of 2 or 3 aerial conductors inclined toward one another at 
angles varying between 45 and 90 degrees, for instance, as indicated 
by a b in Fig. 5 herewith. 

It is known that ah open circuit like the Hertz oscillation rods or 








TRIANGULAR AERIALS. 


245 


like the vertical wire used in wireless telegraphy radiates electric 
waves in every direction or symmetrically; whereas a closed oscillation 
circuit radiates the waves chiefly in the direction of the plane of the 
circuit, as outlined in Fig. 4, in which s is the spark gap and c is a 
capacity. The triangular arrangement of aerial is virtually a closed 
circuit and hence tends to the radiation of electric waves chiefly in the 
direction of the plane of the closed circuit. 

In the published accounts of his experiments Artom states that 
when oscillatory currents of displaced phase are established in con¬ 
ductors arranged in this manner they acquire important directive 
properties, both as regards transmitting and receiving; that in aerials 
so inclined toward each other the mutual induction is very small when 
oscillatory currents flow through them, which fact permits of estab¬ 
lishing absolutely in advance the period to be used in transmission. 
Further, that this inclination of the aerials produces the phenomena 
of composition and interference between electromagnetic waves emit¬ 
ted by two conductors, because it compels a superposition of the re¬ 
spective beams of electric and magnetic lines of force. 

For the reception of electric waves Artom employed the arrange¬ 
ment shown in Fig. 5, in which a b are the two wires arranged as a 
triangle, rn, to' are coils in series therewith and wound in such man¬ 
ner that their inductive effect on the central coil n is nil when cur¬ 
rents of the same direction and strength simultaneously pass through 
them. But currents in either coil alone will induce corresponding 
oscillations in coil n. Hence, when a wave front arrives in the direc¬ 
tion of the plane of a b it falls first on the nearer wire, say, a, as 
indicated by the arrow, setting up an oscillation in to , and after a 
certain interval it falls on wire b, setting up an oscillation in to', 
both of which oscillations act on coil n, the result of which is that a 
detector in the circuit of that coil is operated in the ordinary way. 
But, on the other hand, when a wave front from a direction perpen¬ 
dicular to the plane of a b arrives it falls on wires a b at the same 
instant, as indicated by line c, setting up as before oscillation currents 
of equal strength and direction in coils to to', which currents have no 
effect on coil n, for the reasons stated. Count Artom in 1905 utilized 
this arrangement in determining the position of transmitting stations 
on vessels and on land. For a full account of these experiments see 
“Atti Della Associazione Elettrotenica Italiana, Vol. XII.” 


246 


WIRELESS TELEGRAPHY. 


BELLINI-TOSI DIRECTIVE WIRELESS SIGNAL SYSTEM. 

More recently Bellini and Tosi have introduced an arrangement for 
directive signaling that has met with some practical success in France. 
These inventors began their experiments with a triangular, nearly 
closed aerial circuit capable of rotation on its axis, using a transmitter 
and receptor somewhat similar to those already described. 

In common with other experimenters Bellini and Tosi found that 
the strength of received signals was a maximum when the plane of the 
triangle transmitter circuit was pointed in the direction of the receiv¬ 
ing station, and that upon turning the triangle on its axis, diverting 
its plane away from that station, the strength of signals gradually 
weakened and was always zero when the plane was at right angles to 
that station. The limiting angle for readable signals depended on 
the power employed at the transmitter and on the sensitiveness of the 
detector. 

To avoid, however, the difficulties involved in the use of movable 
aerials for directive purposes Bellini and Tosi have devised the in¬ 
genious plan of employing two sets of triangular aerials, each triangle 
being placed at right angles to the other set, as outlined in Figs. 6, 7, 
8 (in which w e represent the two upper sides of one triangle and 
N s similar sides of the other triangle) ; and in connection with this 
arrangement of aerials they utilize a device termed a radio-goniometer, 
n w c. 

The radio-goniometer consists of two fixed coils n w at right angles 
to one another, and of a central coil c movable on a pivot in any 
direction within the coils n iv. When used for transmission the coil c. 
Figs. 6, 8, is the primary of an oscillation transformer with two sec¬ 
ondaries, n, w. Reversely when used for the reception of signals, as in 
Fig. 7, coil c becomes the secondary of two primaries n w. The fixed 
coil n is connected with the aerial wires n s ; fixed coil w is connected 
with aerial wires w r e. 

When the device is used as a transmitter, if it is desired to transmit 
signals in the direction of the plane of, say, n s, the primary coil c 



RADIO-GONIOMETER. 


247 


is turned on its pivot until it is parallel with coil n, at which time 
inductive effects will be inappreciable in coil w, but will be a maxi¬ 
mum in coil n and the direction of transmission will be n s. Simi¬ 
larly if the primary coil be placed parallel with coil w the direction 
of radiation will be w e. Or if it be desired to send signals in any 
direction between w n or e s, this is effected by placing the coil c 
in the desired position. In the latter case each coil n w will be acted 
upon proportionately to its angle with coil c, and the direction of 
radiation will be a resultant due to the combination of the two electro¬ 
magnetic forces developed by the coils n w, virtually according to the 
law of the parallelogram of forces. In Fig. 6, for instance, with coil 





Fig. 8. 


as shown, the resultant direction would be as indicated by the dotted 
lines r; the length of thick lines n and e, respectively representing the 
assumed magnitude of the component forces in the directions indi¬ 
cated by those lines. Or, if the coil c be turned in the direction of 
dotted or resultant line t, the magnitude of the component force due 
to coil w would be reduced by the amount indicated by the intersection 
of dotted line at t f , while the component force due to coil n would be 
increased by an amount indicated by dotted line n'. For a full ele¬ 
mentary explanation and instances of the operation of this law of 
forces relating to analogous subjects the student may be referred to 
the Author’s “American Telegraphy,” Chapters VII, XIX. 

Eeversely, again, when the radio-goniometer is used as a receiver, 
Fig. 7, the incoming wave fronts will fall on the closed aerial oscilla¬ 
tion circuits, virtually as stated in connection with Fig. 5. If, for 
example, the arriving wave front is in the plane of n s, coil n only 
will be affected and coil c is turned by the operator until maximum 
signals are obtained. If, on the other hand, the wave front is ad¬ 
vancing from a direction midway between n and e, the coils n w will 
















248 


WIRELESS TELEGRAPHY. 


be equally affected and the best position for coil c will be as indicated 
by the dotted line l. 

Ordinarily the radiation in a closed oscillation circuit is in both 
directions, forward and backward, in the plane of the circuit, as indi¬ 
cated by the dotted line r in Fig. 6. To confine the radiation to the 
direction of the receiving station, a vertical wire v, Fig. 8, is con¬ 
nected with the coil v, which is also in inductive relation to the coil 
c. By exciting the coil v and consequently the wire v to a critical 
strength and with a desired phase relation to assist the resultant for¬ 
ward radiation and to annul the backward radiation from the closed 
circuit aerials, the desired result is obtained. 

In practice the transmitting primary coil c consists of a single turn 
of 3 heavy wires in parallel wound on a cylinder pivoted on a vertical 
axis. The two secondaries consist of 10 turns of heavy wire wound at 
right angles on a hollow cylinder, into which the primary is placed. 
Precautions have been taken in the mechanical construction of the 
transformer to insure that the angular displacements of the primary 
and of the direction of transmission shall always be uniformly main¬ 
tained. The system is also arranged for direct or inductive coupling 
to the aerials. 

In the Bellini-Tosi experiments the transmitting station was placed 
at Dieppe, the receiving stations were at Havre and Barfleur. The 
distance from Dieppe to Havre is about 55 miles overland; to Bar¬ 
fleur 105 miles over sea. The base of the triangular aerial used is 
180 feet, the height of the sustaining mast is 160 feet. The sides of 
the triangle consist of a trellis of 9 parallel copper strands, 5 inches 
apart; each strand being composed of 7 No. 19 wires. The distance 
between the upper end of the triangle is 9.75 inches. The wave 
length employed is from 350 to 400 meters. 

Because of the fact that the closed circuit arrangement of aerials is 
a poor radiator of energy Bellini and Tosi found, as anticipated, that 
it is necessary to employ a somewhat greater power than is required 
to signal over a given distance by the ordinary vertical aerials. For 
instance, a maximum of 500 watts was essential for transmission be¬ 
tween the stations mentioned. In view of the advantages of persistent 
oscillations and freedom from atmospheric disturbances obtained by 
the closed circuit arrangement, together with the great advantages of 
directive signaling, the inventors believe that the matter of extra 
power for transmission will be more than compensated by the use of 
directive signaling systems. 


United States Signal Corps Wireless Station, Fairbanks, Alaska. (See page 125) 


ALASKAN WIRELESS STATION 


249 









CHAPTER XVI. 


PRACTICAL APPLICATIONS OF WIRELESS TELEGRAPHY. 

Ik addition to the wireless circuits already mentioned as in opera¬ 
tion, there is one from the Lizard to the Isle of Wight, 186 miles 
distant. There are also systems installed at different points on the 
coasts of European countries—at La Panne, Belgium, for example, 
and at Borkum Island in the North Sea, off the mouth of the 
Ems. Many other lightships and lighthouses have also been equipped 
with wireless outfits, and eventually, no doubt, all lighthouses, light¬ 
ships, and life-saving stations will be constituted wireless telegraph 
stations, whence messages may be signaled to and from passing vessels. 
Hundreds of mercantile steamships have already been equipped with 
wireless outfits, and it has become a common occurrence for such ves¬ 
sels to maintain communication with one another for hours in mid¬ 
ocean. In other instances vessels have been in wireless communica¬ 
tion with one ship or another throughout the entire voyage. Wire¬ 
less stations have also been erected on the piers of some of the large 
Atlantic liners, whereby the outgoing and incoming vessels maybe in 
communication with their agents long after they leave, or before they 
arrive, at their docks. Doubtless, also, within a comparatively short 
period every steam-vessel of any consequence will be similarly equipped, 
and in time all kinds of craft, for the safety of officers and crew, and 
probably as a matter of economy as well, so far as relates to insurance, 
will be equipped with wireless apparatus sufficient at least for the 
purpose of transmitting code signals. 

There is little question that the use of wireless telegraphy on war¬ 
ships will become general in the near future. Already many such 
ships are equipped with the Marconi, Braun, Slaby-Arco, or other 
systems. There are several reasons why such systems are especially 
applicable to and desirable on war-vessels, which depend so largely on 
signaling from ship to ship. In the first place, there is at present no 


USE IN WARFARE. 


251 


other practicable method of signaling at sea to a distance of even a few 
miles in foggy or hazy weather. Further, the officers of such ships, 
as a rule, already have, or can readily acquire, the necessary technical 
skill to successfully operate the system. Again, the vessels already 
carry the necessary masts for the vertical wires, and the apparatus 
and battery, or other source of E. M. F., do not require to be portable. 
These latter features, of course, also apply to mercantile vessels. 

With regard to the use of wireless telegraphy for military purposes 
in actual warfare, the question is somewhat different, and the obsta¬ 
cles to its successful use for this work are considerable. Thus the 
question of obtaining and transporting masts or other suitable sup¬ 
ports for the antenna is a serious one. This has already been found 
a difficulty in actual warfare in South Africa. Apparently captive 
balloons or kites have not been altogether suitable for this purpose, 
although such balloons have been used with some success in experi¬ 
mental work. In recent tests, signals have been transmitted from 
Portsmouth to Aldershot, England, about 70 miles inland, a captive 
balloon being employed at the last-named station. There is also the 
fact to be considered in this relation that signaling overland by elec¬ 
tric-wave telegraphy is not as feasible as 'over water. It may be 
remarked in passing, that experiments by Fessenden have indicated 
that transmission over salt water is thirty times better than over fresh 
water. As noted elsewhere, distances of from 15 to GO miles overland 
have been covered, but not always with satisfactory regularity. Even 
a distance of 15 to 30 miles would doubtless be a very valuable addition 
to military signaling in warfare. (See page 101.) There is, however, 
nearly always in land operations the alternative of wire telegraphy; 
and while the difficulties of transporting the poles or light rods and 
wire for overland wire telegraphy are frequently very great, they have 
rarely been found insurmountable, and where this may bo the case, 
as when the enemy is between a relieving army and a beleaguered 
garrison, it is not unlikely that the enemy, by keeping up a cross-fire 
of electric waves, could prevent communication by means of wireless 
telegraphy. It may be noted that heliography was successfully main¬ 
tained between the British relieving army and the Ladysmith garrison 
during the late South African war. A wireless telegraph system is 
now being installed in Alaska for the United States Signal Corps* 
This will probably be the most extensive overland system thus far 
established, and its progress will be watched with interest. It will 


252 


WIRELESS TELEGRAPHY. 


extend from Fort Gibbon to Cliena, 200 miles, with an intermediate 
station at Tolovana, on the Tanana River. All of these stations are 
army posts. The United States government (or its various depart¬ 
ments) has also experimented with the Marconi, the Fessenden, the 
De Forest, the Slaby-Arco, and Braun systems, at different places 
in this country. 

It is proposed by Dr. Scholl to employ wireless telegraphy in con- 
nection with an expedition to the North Pole which is being organ¬ 
ized in Munich. The plan includes a station equipped with the Braun 
system on Spitzbergen Island, of sufficient capacity to enable com¬ 
munication to be maintained with the exploring vessel, on which will 
be a similar wireless outfit. 

Considerable progress with wireless telegraphy is reported from 
Japan. The first experiments were made between Yawata and Funa- 
bashi, a distance of eleven miles overland, and, afterward, between 
the shore and war-ships in Tokyo Bay, when a distance of twenty miles 
was covered. A large wireless plant is now being constructed, at a 
cost of over $10,000, to operate between Japan and an island off For¬ 
mosa, a distance of 850 miles. The system employed in Japan is due 
to a native of that country, and has not been described. 

The attempt to utilize wireless telegraphy to and from moving 
trains has been tested in Canada and in Germany. In the German 
tests the conducting wire on the train was carried on insulators along 
the eaves of the cars, and the waves employed were 656 feet in length. 
The oscillations were transmitted to and from the cars on special wires 
which were strung on the telegraph wires along the track. The oscil¬ 
latory currents did not disturb the signals passing on the contiguous 
telegraph or telephone wires, although a crackling sound was heard 
in the telephone. On the other hand, the wireless system was at 
first badly disturbed by the telegraph signals, the sparks at the open¬ 
ing and closing of the telegraph keys setting up oscillations that 
traveled along the conductor and affected the coherer. This defect 
was remedied by shunting the telegraph keys with non-inductive 
resistances. It may be added that there was no demand for a service 
of this kind in this country when it was offered in the shape of induc¬ 
tion telegraphy. (See page 11.) 

Tim utilization of wireless telegraphy when overland telegraph 
lines have been prostrated by violent storms has also been suggested. 
This, however, presupposes that the masts or towers of the wireless svs- 


OBSTACLES TO WIRELESS SIGNALING, ETC. 253 

tem would be left intact at such times, which might not always be the 
case. In any event, until it is practicable to multiplex wireless tele¬ 
graph circuits, the wireless system in such cases could only be availed 
of to a somewhat limited extent, which, however, might, at times, be 
of vast importance. In this relation Professor Fessenden points out 
that during the years 1900, 1901, 1902, there was no interruption of 
the wireless service on which his system is employed between Cape 
Ilatteras and Roanoke Island, with masts 125 feet high; and between 
Fortress Monroe and Cape Charles City, Virginia, with masts 50 feet 
high. In the same period the telegraph and telephone wires were 
frequently down during severe storms. The same writer also states 
that with sharply selective systems there is no trouble from atmos¬ 
pheric electricity, but with non-selective systems the receivers, if 
directly in the aerial circuit, are liable to burn out; this is not the 
case, however, with liquid detectors. On the circuit last referred to 
the speed of transmission is reported to be about 25 words per minute. 

The extreme distance to which signals may be transmitted by wire¬ 
less telegraphy with sufficient accuracy and reliability to meet com¬ 
mercial requirements is not yet definitely determined. Every day 
sees improvements in large and small details, but it is too early to 
expect that the end of improvement in wireless telegraph apparatus 
has yet been reached. There are also to be overcome the interference 
from neighboring wireless systems as well as the variations in the sig¬ 
naling distances that are found to occur in practice, and which may 
be due to atmospheric changes or other causes; and also the variations 
in signaling distances between day-time and night-time, instances of 
which have already been given (page 73). The interferences from 
neighboring wireless systems will be overcome when successful syntony 
is accomplished (and improvements in methods and apparatus are 
rapidly advancing this feature of the art), and by an agreement 
between the different companies to adhere to prescribed wave-lengths. 
Tuning, however, will not avoid interference where the gamut of 
electrical oscillations is run by electric sirens in the neighborhood of 
receiving stations. (See page 13 for an instance of a variable-period 
generator.) 

To obtain the best results when wireless telegraphy is employed 
for the regular commercial handling of business, it will also be neces¬ 
sary that the transmission and reception of messages shall go on simul¬ 
taneously from the same stations. Devices for this purpose have been 


254 


WIRELESS TELEGRAPHY. 


patented by Fessenden and others. The variations in the signaling 
distance due to the effect of daylight may be measurably overcome 
by increasing the strength of transmitted signals or by increasing 
the sensitiveness of the receiver. To overcome the variations caused 
by atmospheric conditions which are more or less obscure will doubt¬ 
less bo more difficult. Captain II. B. Jackson, in a series of experi¬ 
ments on shipboard in the Mediterranean, noticed that a sirocco wind, 
holding moisture, salt, and dust in suspension, absorbs the electric 
waves to a great extent. Lightning flashes, he observed, always pro¬ 
duce signals, and occasionally spell words in the Morse code, though 
the usual record is e i. Fessenden, on the other hand, states that 
with sharply selective systems the severest thunder-storms do not 
prevent the transaction of business, but occasionally a word is lost. 
Jackson also found, in signaling at sea across intervening land, that 
some waves pass through, over, and possibly round the land, but in 
doing so their energy is reduced to an amount depending on the 
length, height, and nature of the obstruction. In one instance, where 
an extremely precipitous and narrow promontory 800 feet high, con¬ 
sisting of hard rock containing iron ore, intervened between the 
transmitter and receiver, the signals were at once cut off, although 
over the open sea signals were readily exchanged at a distance of 
45 miles under otherwise the same conditions. 

In order that the advantages of wireless telegraphy may be secured 
to the largest extent in the matter of preventing collisions between 
ships at sea, for obtaining assistance, etc., when necessary, which are 
popularly supposed to be the uses to which this system is especially 
adapted, and in which it has already demonstrated its utility in numer¬ 
ous instances, it seems evident that the apparatus will have to be more 
or less simplified and improved as to reliability, especially as regards 
the sources of the oscillations. At present, it may be admitted, the 
apparatus requires an amount of skill in the handling that is not avail¬ 
able on small craft. On the larger vessels a special operator may be 
employed, as is now the custom, and on steam-vessels of medium size 
the work of caring for the apparatus could be delegated to some of the 
junior officers. Doubtless a knowledge of the manner of operation of 
wireless apparatus will ultimately be made one of the essential qualifi¬ 
cations of such officers. To meet the requirements of the larger vessels 
and important land stations in the matter of expert operators, more 
than one of the wireless telegraph companies have already established 


WIRELESS SCHOOLS, ETC. 


255 


training schools in this country and Europe, where pupils are taught 
the Morse alphabet, and are also given instruction in every detail of 
the operation of each piece of apparatus employed in the system. 
They are also instructed how to detect and remedy any defects that 
may occur in the apparatus, and to make any ordinary repairs that 
may be necessary. The time for this tuition varies from four to eight 
weeks, depending on the aptness of the pupil. This, it will be under¬ 
stood, refers to instruction in receiving by the Morse ink recorder, 
which is quickly learned. To learn to receive by sound requires a 
longer time. 

For simple code signaling, of course, the amount of skill required 
is a minimum and can be supplied by aiiy one capable of manipulating 
the marine flag code. There still remains, then, the simplification 
of the apparatus if the system is to be adapted to vessels of all 
kinds, to lightships, lighthouses, life-saving stations, etc. A long 
step in this direction would he the displacing of the primary or 
storage battery and interrupter by some form of manually operated 
source of E. M. F. of sufficient power to cover a distance of, say, five 
to ten miles, which for all ordinary purposes of code signaling would 
be ample. The received signals in this case would consist of the ring¬ 
ing of a bell, or tapping of a sounder, operated by the coherer relay 
a prearranged number of times for any given message. In cases of 
fog at sea the simple ability to ring a bell at intervals on a neighbor¬ 
ing ship would serve at least to place the officers of the vessels on the 
alert. A still further simplification of apparatus and methods will 
doubtless ensue should wireless telephony become an assured success; 
although for some purposes, as when vessels of different nationalities 
require to communicate with one another, a system in which the uni¬ 
versal code signals could be employed will perhaps be of the greatest 
general utility. 

Various uses of wireless telegraphy are announced almost daily in 
the public press, such as the actual sending of money orders from one 
ship to another, playing chess by sending the moves by wireless, etc., 
which are on a par with analogous announcements that were wont to 
be made to excite the wonder of the public in the early days of wire 
telegraphy, such as the recapture of an escaping criminal by means of 
the telegraph; but it is obvious that such happenings are natural inci¬ 
dents in any form of telegraphy, wireless telegraphy’s part being to 


256 


WIRELESS TELEGRAPHY. 


augment the sphere of usefulness of the telegraph, which it has 
already done to a very important degree. 

Thus far wireless telegraphy has found its highest degree of use¬ 
fulness in the transmission of intelligence between vessels at sea, 
between vessels and the mainland, between points divided by the sea, 
or between certain localities overland where it is not feasible or profit¬ 
able to lay a cable. Transatlantic wireless telegraphy, or cableless 
telegraphy, as it has been called, is not yet (1904) an accomplished 
fact, considered from a commercial standpoint. As intimated in the 
preceding pages, considerable work has actually been done in the 
effort to establish wireless telegraphy as a competitor of wire teleg- 
graphy between points where the latter is already in successful opera¬ 
tion, but not with marked success. Perhaps these attempts are not 
yet desirable. Wireless telegraphy has a special field for which it is 
preeminently adapted, and into which, in the nature of things, wire 
telegraphy cannot enter. It may develop that the reverse of this 
is measurably true, and that the field covered so successfully by wire 
telegraphy is one which the wireless system is not so well adapted to 
enter, but the present writer is not so unwise, in the light of what 
has been accomplished in the past in the art of electrical telegraphy, 
as to place any limitations on the possible applications of wireless 
telegraphy. _ 

The application of wireless telegraphy to automatic fire-alarm tele¬ 
graph purposes has also been proposed, and M. Guarini has experi¬ 
mented with apparatus designed therefor. The apparatus at the 
protected building consists of the usual induction coil, spark-gap, and 
vertical wire. A thermostat consisting of a tube containing mercury 
controls a local circuit. When the temperature at the tube exceeds 
a predetermined point the local circuit is closed, the closing of which 
operates an armature that releases a break-wheel which at once revolves, 
thereby opening and closing the induction-coil circuit, with the result 
that a certain number of high potential impulses are thrown upon 
the vertical wire. These in turn affect a coherer at the firemen’s 
headquarters, giving the alarm, the number of transmitted signals 
indicating the location of the protected building in the well-known 
manner. (See Chapter XXVIII. author’s “ American Telegraphy and 
Encyclopedia of the Telegraph.”) 



SPECIAL WIRELESS CALLS. 


257 


At the present time (opening of 1910) nothing has developed to 
contradict the views expressed in the foregoing section relative to 
the anticipated progress of wireless telegraphy. This art in fact 
has now found its place as a reliable means of communication 
between ships at sea, and ships and the shore, in which capacity it 
has more than once quite recently demonstrated its paramount 
importance in bringing prompt assistance to vessels in distress. 
This result has given added impetus to the already existing demand 
that at least all passenger carrying ships shall be equipped with 
wireless apparatus. But apart from the value of wireless telegraphy 
in times of danger its utility in placing the owners in communication 
with their ships on nearing shore, to receive or give instructions, 
together with the convenience that it affords in placing the pas¬ 
sengers of such vessels in touch with their friends ashore, is of itself 
in most cases sufficient to warrant the installation of the apparatus 
and the employment of an attendant for its operation. 

The generally accepted signal for aid in case of great danger at 
sea in American waters has been “C. Q. D.” This call has been 
abused on more than one occasion by would-be practical jokers, not 
possessed of sufficient intelligence to realize the gravity of the 
offense. Partly in consequence of this, and also to obtain a uni¬ 
form danger signal the call in use in Europe for several years for 
this purpose may hereafter be employed. Namely “S. 0. S.”, 
(3 dots, 3 dashes, 3 dots). A message to all stations is indi¬ 
cated by the signal “CQ.” The call in Europe for a “rest” or 
stopping of signaling, consists of 6 dashes. When this signal is 
sent by any coast station all ships are required to cease signaling. 
A “search” signal consists of 3 dots, 3 dashes. This signal followed 
by the name of ship sought for, is repeated until the ship answers, 
“Here.” The German regulations require that all stations before 
commencing a call must adjust the receiver, to its highest point of 
sensitiveness to avoid interference with messages already in process 
of transmission. The signal “99” is used in this country when an 
emergency message is to he sent to a station, on hearing which all 
other stations are expected to refrain from interference. 

If any one should be disposed to question the extent to which 
wireless telegraphy is now in actual operation, his doubts may be 
dispelled by employing a simple wireless receiving set and a crude 
aerial, consisting of 100 or more feet of No. 20 B & S wire (height 
about 50 feet) and by means of which the continual passing of wire¬ 
less messages may be detected; three, four and more messages often 
•being in transit at the one time, day and night; separated from one 
'another on any given receiver by variations in strength or frequency. 
The following somewhat typical messages were in this way recently 
drawn by the writer from the ether waves, on the New Jersey coast, 
the names only being changed: To “John Amos, Neighborhood 
Association, Sands Street, Brooklyn. Will dock at nine tomorrow 
morning. John.” “Philadelphia, August 27, 1909. To Miss P. E. 
Saxson, Str. Harvard. Pleasant and safe trip on your homeward 
journey. Kindest regards from Bellevue-Stratford. W. II. Pilson.” 


258 


WIRELESS TELEGRAPHY. 


Following is a partial list of calls of Atlantic, Pacific, and other 
coast and ship-board stations: 


Annapolis, Md., Naval Academy.QG 

Atlantic City, N. J.AX 

Beaufort, N. C.QS 

Boston, Mass. (Navy Yard) .PG 

Baltimore, Md.B 

Brant Rock, Mass.BO 

Brooklyn Navy Yard .PT 

Bridgeport, Conn.BG 

Cape Cod (Wellsfleet) .CC 

Cape Cod (North Truro) .PH 

Cape Elizabeth, Me.PA 

Cape Hatteras .HA 

Cape Henolopen, Del.PX 

Charleston, S. C. (Navy Yard) .SN 

Colon, Canal Zone .SL 

Diamond Shoals Lightship .QP 

Elizabeth City, N. J.HD 

Fire Island, N. Y.PR 

Fort Totten, N. Y.FT 

Fort Wood, N. Y.FD 

Galilee, N. J.G 

Galveston, Tex.GV 

Isle of Shoals, N. H.A 

Jupiter Inlet, Fla.RA 

Key West, Fla. (Naval Station) .RD 

Key West, Fla.KW 

Manhattan Beach, N. Y.DF 

Mobile, Ala.MB 

Nantucket Shoals Lightship .PI 

New Orleans, La., Naval Station .DO 

New Orleans, United Fruit Co.HB 

New Orleans, Unitel Wireless _TC. HK 

Newport, R. I., Torpedo Station .PK 

New York City (Waldorf-Astoria)... .WA 

New York City (42 Broadway) .NY 

New York City (Hotel Plaza) .FS 

Norfolk, Va. (Navy Yard) . QL 

Norfolk, Va. (Public) .N 

Pensacola, Fla. (Navy Yard) .RK 

Philadelphia, Pa. (Navy Yard( .PV 

Philadelphia, Pa. (Bellevue-Stratford) BS 

Point Judith, R. I.PJ 

Port Arthur, Tex.RV 

Portsmouth, N. H. (Navy YardJ.PC 

Savannah, Ga.SV 

Sea Gate, N. Y.MSE 

Siasconsett, Mass.MSC 

Southwest Pass, La.SW 

St. Augustine, Fla.QX 

Tampa, Fla. ...PD 

Washington, D. C. (Navy Yard) .QI 

Wilmington, Del.DU 

Wilson’s Point, Conn.WN 

Cape Blanco, Oregon .TA 

Everett, Wash. DK 

Farallon Islands, Cal.TH 

Honolulu .UC 

Guam Island .UK 

Fort Warden, Wash.FW 

Los Angeles, Cal.(G) (PJ) 

Mare Island, Cal.TG 

Pasadena, Cal.DE 

Portland, Oregon .PE 

Puget Sound, Wash.SP 

San Francisco, Cal.SF 

Table Bluff, Loleta, Cal.TD 


Tacoma, Wash. 

Tatoo'sh Island, Wash. 

Yerba, Buena Island, Cal. 

Cordova, Alaska . 

Nome . 

Sitka . 

Belle Isle, Que. 

Battle Harbor, Labrador . 

Cape Bear Lighthouse, Pr. Ed. Isl 

Fame Point Lighthouse, Que. 

Father Point, Que. 

Point Amour, Que.. 

Whittle Rocks, Labrador . 

Heath Point, Anticosti . 

Cape Race, N. F.. 

Cape Ray, N. F. 

Cape Sable, N. S... 

Cape Rich, N. S. 

Halifax, N. S. 

Sable Island . 

Sidney, Cape Breton . 

Quebec, Que. 

Picton, N. S. 

Borkum, Germany . 

Borkum Reef, Germany . 

Elbe Lightship, Germany . 

Heligoland, Germany . 

Dover, England . 

Holyhead, England . 

Lizard . 

Niton . 

Gibraltar . 


...PB 

...SV 

...TI 

...SN 

...SA 

...SO 

...BL 

..BH 

...BF 

...FP 

...RT 

...PR 

..WR 

..HP 

...CE 

...CR 

...SB 

...TC 

MCN 

MSD 

..ND 


KBM 
.FBR 
.FEF 
KHG 
DDD 
..HD 
...LD 
...Ul 
, .GIB 


SHIPS. 


New York (Amn.) .MNK 

Philadelphia (Amn.) .MPH 

St. Louis (Amn.) .MSL 

St. Paul (Amn.) .MSP 

Lusitania (Cunard) .MFA 

Mauretania (Cunard) .MGA 

Lucania (Cunard) .MLA 

Minnehaha (A. T. L.) ^.MMA 

Minneapolis (A. T. L.) .MMS 

Virginian (Allan) .MGN 

Victorian (Allan) .MVN 

Tunisian (Allan) .MTN 

Arabic (W. S. L.) .MCF 

Cedric (W. S. L.) .MDC 

Deutschland (H.-A. L.) .DDL 

President Lincoln (H.-A. L.) .DDT 

President Grant (H.-A. L.) .DDS 

K. Wilhelm der G. (N. G. L.).DKW 

K. Wilhelm II. (N. G. L.) .DKM 

Kronpr. Cecille (N. G. L.).DKA 

Bremen (N. G. L.) .DBR 

Caledonia (Anchor L.) .MAP 

Columbia (Anchor L.) .MOI 

Furnesia (Anchor L.) .MFI 

Bermudian (Que. Line) . BA 

Trinidad (Que. Line) .BD 

Momus (So. Pac.) .KM 

Yale (Met. Line) .RY 

Harvard (Met. Line) .RH 

Plymouth (N. E. Nav.) .HY 

Priscilla (N. E. Nav.) .CA 


A very full list of the wireless telegraph stations of the world is given in a pamph* 
let issued by the Navy Department, Washington, D. C. 






























































































































CHAPTER XVII. 


AMATEUR DEPARTMENT. 

ELECTRIC OSCILLATIONS AND CIRCUITS—AMATEUR WIRELESS STATIONS 

-WIRELESS APPARATUS-AERIALS—NOTES ON TUNING, ADJUST- 

' MENT OF APPARATUS, ETC. 

To-day there are thousands of amateur wireless telegraph stations 
in different parts of this country, and the number is constantly grow¬ 
ing. Some remarks appertaining more particularly to the needs of 
amateurs than what have preceded may therefore not be amiss. 

It is well known that wireless telegraph signals are transmitted by 
means of electric waves that are set up by electric oscillations in a 
vertical wire or wires, usually termed the aerial, or antenna. During 
the occurrence of these oscillations in the transmitting aerial, electric 
energy,- in some way not yet well understood, is radiated from the 
aerial, in the form of electromagnetic waves in the ether of free space. 
These waves on reaching the receiving aerial set up therein corre¬ 
sponding oscillations (usually very minute as compared with the 
transmitted oscillations) that affect the wireless detector, and the 
transmitted signals are thereby reproduced. 

The ether may be regarded as an intangible, all-pervading some¬ 
thing in which we are able to set up waves of many kinds—light 
waves, heat waves and electric waves—and analogously as ever ex¬ 
panding waves are set up in a mill pond bv dropping a pebble into it, 
so by suitable means we may set up, as just stated, electromagnetic 
waves in the ether that travel away from their source with the speed 
of light. 

It may aid to an understanding of this general subject on the part 
of beginners if the idea is grasped that electric oscillations in the 
transmitting and receiving aerials are simply alternating currents, 
that is, ordinary electric currents, surging back and forth in a cir¬ 
cuit hundreds, of thousands or millions of times per second. Since 
there cannot be an electric current without electromotive force 
(e. m. f.) and since a current cannot flow in a straight conductor 


260 


WIRELESS TELEGRAPHY. 


without setting up magnetic lines of force, and since also rising and 
collapsing magnetic lines of force in or near a conductor tend to 
establish an electric potential in the conductor, it is evident that these 
high frequency electric oscillations, like ordinary low frequency elec¬ 
tric oscillations or alternations, must be accompanied by the phe¬ 
nomena of magnetic and electric lines of force. 

It is well known that if a bar magnet be drawn rapidly through 
the center of a coil of wire an e. m. f. is set up in the wire due to the 
“cutting” of the wire by the moving magnetic lines of force. This is 
the principle of operation of a dynamo machine, except that the mag¬ 
netic lines of force are stationary, while the coils of the armature in 
turning cut the lines of force. As stated on page 7, Chapter I, when 
a conductor receives a charge of positive or negative static electricity 
(the electric component of the electromagnetic wave) a momentary 
current is set up in the conductor. Each electromagnetic wave in the 
ether is assumed to consist of an electric and a magnetic force or com¬ 
ponent, each component possessing an equal amount of energy. Ac¬ 
cording to the generally accepted theory, as these waves emanate 
from a vertical wire, the magnetic component thereof is at right angles 
to the vertical wire, while the electric component of the wave is in the 
vertical plane of the wire. Thus if a section of each component of a 
wave were shown on this page, the magnetic force would be repre¬ 
sented by a horizontal dash, the electric force by a vertical dash. 

When,’ then, an electromagnetic wave reaches a receiving vertical 
wire the magnetic or horizontal component of the wave at right angles 
to the wire cuts it and sets up a momentary e. m. f. therein, and when 
the electric or vertical component or force reaches the wire it imparts 
an electric charge to that wire, and in either case electric oscillations 
are set up in the wire. The wave meantime passes on with a rent or 
tear in its contour, or wave front, corresponding to a shadow thrown 
by an obstacle in the path of light. Wave after wave reaches the 
vertical wire, each wave giving up a portion of its energy thereto, and 
if the oscillation period of the aerial is in accord with that of the 
oncoming waves the effect of each succeeding wave will tend to be 
cumulative in the wire. Hence the desirability of tuning the aerial 
for receiving signals. For a rough working idea of the action of an 
electromagnetic wave, however, it will suffice to assume that the wave 
has but one component, virtually as a simple water wave has but one 
component, and, in general, for practical purposes the analogy of an 


ELECTRIC OSCILLATIONS. 


261 


advancing water wave may be utilized in this relation. (See remarks 
on Figs. 1, 2, Directive Wireless Radiation.) It may be noted that 
the atmosphere plays no part in the propagation of wireless telegraph 
signals, except in so far as it may at times carry ionized, or electrified, 
particles that disturb the ordinary propagation of the electric waves in 
space. 


ELECTRIC OSCILLATIONS AND CIRCUITS. 

In wireless telegraphy there are placed in the secondary circuit of 
an induction coil, or transformer, (a) a condenser (capacity), (b) a 
coil or helix of wire termed an inductance, and (c) a spark gap; and 
inductively or directly connected with this circuit an aerial or vertical 
wire. The electrical properties of capacity and inductance are de¬ 
scribed on pages 19, 20. As just noted herein, electric oscillations are 
simply electric currents alternating in direction in a circuit. These 
currents in the case assumed are set up by the induction coil. The 
operation and construction of this coil are based on the principle of 
electromagnetic induction whereby a current passing in one wire in¬ 
duces current in a neighboring parallel wire. (See Page 6.) In¬ 
duction coils consist of two coils of wire termed the primary and sec¬ 
ondary wires; the primary consisting of a small number of turns and 
the secondary of a large number of turns. Consequently, when the 
current in the primary circuit is interrupted rapidly the e. m. f. of 
the primary develops a much higher e. m. f. in the secondary. Or the 
reverse of this is true; if the turns of the primary are many, while 
those of the secondary are few, the e. m. f. of the primary is, as it 
said, stepped down, in the secondary. The manner in which the in¬ 
terruptions are made in the primary circuit and in which alternating 
currents are set up in the secondary of the induction coil is described 
in Chapter II. Details of construction of an induction coil are given 
subsequently. 

In Fig. 1 is shown a simple wireless telegraph transmitter circuit. 
It is divided into three, or, we might say, four separate circuits. 
Namely, (1) the primary circuit of b , p, i. consisting of the power 
battery b, the primary of the induction coil p, and i the interrupter of 
the primary circuit; (2) a circuit consisting of the secondary s of the 
induction coil, and of sg the spark gap; (3) the primary oscillation 
circuit consisting of the spark gap, the condenser c' and an indue- 


262 


WIRELESS TELEGRAPHY. 


tance l; (4) the aerial, or secondary oscillation, circuit, consisting of 
the secondary l' of oscillation transformer (ll') and the aerial wire 
a. ic is the iron core of the induction coil, k is a Morse telegraph 
key. c is a spark preventing condenser of the interrupter i. 

The ultimate object of this arrangement of circuits is to establish 
electric oscillations in the aerial circuit. This is accomplished as fol¬ 
lows. When the key k is closed rapid makes and breaks of the pri¬ 
mary circuit (1) occur at the interrupter i. This develops alternating 
currents in the secondary circuit of the induction coil, in which is the 
spark gap sg. The spark gap should be so adjusted that when the 
potential, or electrical pressure, of a given alternating current reaches 
its maximum (for it must be remembered that the potential starts at 



Figs, i, 2.—Wireless Transmitting and Receiving Circuits. 


zero and rises more or less gradually to maximum) the air resistance 
in the spark gap will break down. The effect is sometimes better if 
the adjustment is such that the spark gap breaks down just before 
the alternation reaches its maximum. (It may be remarked here that 
there are two alternations of current in a complete cycle—a negative 
and positive alternation. That is, in each cycle the current rises 
from, say, zero positive to maximum positive, and falls to zero; thence 
to negative maximum and back to zero. Thus there are four varia¬ 
tions of current and two alternations of current in a cycle.) (See 
remarks on Transformers, Chapter XIV.) Xow at the time when a 
given alternation is rising to maximum and is, so to speak, preparing 
to break down the spark gap it is at the same time also charging the 
condenser c in circuit 3. Briefly, the operation of the electrical con¬ 
denser is based on the fact that when an insulated conductor is 
























CONDENSER DISCHARGES. 


263 


charged with electricity from any suitable source it appears to ex¬ 
cite or induce in any neighboring conductor an equal and opposite 
charge of electricity. Thus, if two metal plates a, b are placed near 
to, but insulated from one another, and the positive pole of a battery 
be connected to one of the plates a, a charge of negative electricity 
will be induced in the other plate b, it being assumed that the nega¬ 
tive pole of the battery and the plate b are connected to earth or by 
a wire. (See page 6.) It is a property of condensers that when they 
are charged and then allowed to discharge through a suitable circuit, 
one in which the resistance is not excessive, the energy of the charge 
expends itself in oscillating back and forth in the closed circuit, some¬ 
what like the pendulum mentioned on page 18 (See page 20 also) ; or 
like the plucked tuning fork cited on page 47. Hence, in the case in 
point, when the spark gap breaks down, the gap becomes virtually 
short circuited by reason of the hot air and vapor, and the con¬ 
denser c discharges itself in a rapid series of oscillations, back and 
forth through circuit 3. 

Reverting to circuit 3 of Fig. 1. It will be noticed that the in¬ 
ductance L, which is here arranged as an oscillation transformer, or 
induction coil, has its secondary i/ in series in the aerial wire. When, 
tnen, the spark gap breaks down and oscillations are set up in circuit 
3, as stated, the primary inductance l acts inductively upon the sec¬ 
ondary wire i/, thereby setting up corresponding oscillations in the 
aerial oscillation circuit 4, and these oscillations acting upon the ether 
of free space, as already noted, lead to the radiation of electromagnetic 
waves, which travel away from the vertical wire with the speed of 
light, in round numbers about 186,000 miles, or 300,000,000 meters, 
per second. Various hypotheses have been offered explanatory of the 
manner in which these waves are propagated in the ether, and the 
reader interested may refer to Chapter V for some information on this 
point. 

On reaching the receiving aerial wire A, Fig. 2, the electromagnetic 
waves of the ether impart some of their energy to that wire, and elec¬ 
trical oscillations are now established in it. These oscillations in 
passing to and fro through the primary coil l of the receiving oscilla¬ 
tion transformer t' set up magnetic lines of force which act in¬ 
ductively upon the secondary coil V, and oscillations are thereby set 
up in the receiver oscillation circuit V c, with the result that the de¬ 
tector d is affected, and sounds are heard in the head telephone re- 


264 


WIRELESS TELEGRAPHY. 


ceiver t. An electrolytic detector d is indicated in the figure. In 
subsequent diagrams it will be seen that a modification of the oscilla¬ 
tion transformer l V is shown, for instance, tc, Fig. 3. This is vir¬ 
tually an auto transformer and the E. M. F. thrown upon the aerial by 
it depends in a measure on the number of turns of the coil tc brought 
into action by the sliding contacts 2, 3. As noted in Chapter XIV, 
when the oscillation transformer l V is employed the oscillation cir¬ 
cuit is said to be inductively coupled to the aerial (loose coupling) ; 
when the auto transformer is employed the oscillation circuit is said 
to be directly coupled to the aerial (close coupling). 

Keference has been already made to the manner in which a tuning 
fork vibrates, page 17. Similarly a metal reed if held at one end and 
hit a smart blow will vibrate to and fro at its fundamental rate of 
vibration, and both the tuning fork and the reed will give forth a tone, 
audible if the rate of vibration is within the range of susceptibility of 
the ear. The fundamental note of a tuning fork or a reed depends 
on its length, thickness, elasticity, etc. If either of these factors be 
varied the rate of vibration will vary. The rate of vibration of a 
reed is also variable in other ways, for instance, by means of a weight 
movable up or down on the reed; this varying the inertia of the reed. 
A rather neat way of varying the inertia of a vibrating armature to 
vary its rate of oscillation may be seen in the Cuttriss siphon re¬ 
corder described in the Author’s “American Telegraphy,” page 270. 
In this the vibrating armature carries vertically a small glass tube 
containing glycerine. A narrow rubber tube conveys the glycerine 
to the vertical tube from a reservoir, and by means of a plunger the 
liquid is raised or lowered in the glass tube, while the armature is in 
motion, until the desired rate of vibration is obtained. 

Analogously the rate of oscillation or tuning of an electric circuit 
containing the equivalents of mechanical elasticity and inertia, 
namely, static capacity and inductance, may be varied by varying 
either of those factors. In the variable tuning coils and variable con¬ 
densers employed in wireless telegraphy we have a simple means of 
varying the frequency and consequently the wave length of the trans¬ 
mitted and received oscillations. In Fig. 3, for instance, the wave 
length of the transmitter oscillation circuit may be varied by moving 
the sliding contacts 2, 3, along the tuning coil tc, or by adding more 
or less capacity to the circuit by means of the glass plate or Leyden 


WAVE LENGTHS. 


265 


jar condensers c, nntil the hot wire ammeter hw shows the maxi¬ 
mum strength of current in the circuit. This is done by, let us say, 
adding more and more capacity to the circuit, until, after the cur¬ 
rent has reached a certain strength, it begins to recede. This implies 
too much capacity, whereupon capacity is reduced. Or similarly the 
inductance may be varied until the same results are observed and ob¬ 
tained. Similarly, too, the frequency of the oscillations of the re¬ 
ceiver circuit may be varied by varying the inductance of the tuning 
coil rc of Fig. 3, or by varying the capacity of c. Further allusion 
to the methods of obtaining tuning will be made subsequently. 

It is customary to term the to and fro high frequency electric cur¬ 
rents in a circuit, electric oscillations. When the energy of oscilla¬ 
tions is transformed into electromagnetic effects in the ether they are 
termed electromagnetic waves. The length of an electric oscillation or 
wave may be ascertained when the capacity and inductance of the 
circuit are known. For instance, it is demonstrable by mathematics 
that the time period, that is, the time during which a complete oscil¬ 
lation lasts, is equal to 6.28 times the square root of the product of 
the capacity and inductance of a circuit, according to the formula 
t = 27 tVkl. Here t is the time period in microseconds, that is, 
the duration of a single oscillation; l is the inductance of the circuit, 
and n (Greek letter pi) the symbol representing the ratio of the 
circumference of a circle to its diameter, namely, 3.1416, and, hence 
2 7 i = 6.28. This is equivalent to saying that the square root of the 
said product must be multiplied by 4 times one-fourth of the said 
ratio. (This remark is elaborated somewhat in the Author’s “Amer¬ 
ican Telegraphy,” Chapter VI.) Knowing, then, as stated, the fac¬ 
tors k L, in microfarads and microhenrys, respectively, which are 
measurable, of a circuit, the frequency and wave length of the oscil¬ 
lation, or corresponding wave, are readily deducible. For, the time 
period of an oscillation being known in microseconds, it follows that 
the frequency n (number per second) of the oscillations or waves will 
equal T, that is, one second divided by the time period of the oscil¬ 
lation. Suppose, for example, that a tuning fork makes a complete 
vibration, or cycle, in the one-hundredth of a second (t), it is evident 

there will be — = 100, that is, one hundred vibrations per second. 

.01 

Similarly, if an electric oscillation occurs in the one-millionth of a 



266 


WIRELESS TELEGRAPHY. 


second (t) in a circuit, it is clear there will be one million such oscil¬ 
lations in one second. Frequency is therefore represented by the 
formula n — 2n ^Akl; since 2n \/k l = t, and ^ equals the num¬ 
ber of oscillations per second. 

Knowing the velocity of electricity, namely, 186,000 miles per sec¬ 
ond, or (adopting the meter unit now so generally employed in wave 
length measurements, 300,000 kilometers or 300,000,000 meters, per 
second), it is clear that the w r ave length will equal th^ velocity v 
divided by the frequency n, namely 300,000,000 -4- 2n yTL (or by 
substitution), wave length = t y L = 2tty's/k l. Then per¬ 
forming the foregoing division we get the comparatively simple 
formula for finding the wave length of a circuit, namely, wave length 
= 1884.90 Vkl the answer being in meters. The expression y'K l 
is called the oscillation constant. The capacity and inductance of an 
oscillation circuit can be measured separately by comparison with 
standard condensers and inductances, the methods of which measure¬ 
ments are described in text-books. In Mr. Pickard’s table of wave 
lengths at the end of this section (which he has kindly given the 
Author the right to use herein) the wave lengths, frequencies and the 
product of the capacity and inductance are supplied. To obtain the 
oscillation constant referred to, the square root of the product kl 
given in the table must be found; which when multiplied by the con¬ 
stant 1884.96 gives the wave length in meters. 

Theoretically the wave length of a single wire aerial is found to 
be somewhat more than 4 times the length of the aerial from its top 
to instruments, but for ordinary practical purposes the wave length of 
the oscillations is roughly taken as equal to 4 times the length of the 
aerial. For an explanation of this see page 35. 

AMATEUR WIRELESS STATION. 

The simplest types of early wireless telegraph apparatus are de¬ 
scribed herein, pages 53, 54. These consist of an ordinary induction 
coil, and a spark gap connected directly in series in the aerial circuit 
at the transmitting station; and of the coherer, relay and tapper at 
the receiving station. For the beginner this arrangement of ap¬ 
paratus and circuits sometimes suffices, but as he progresses with his 
experiments he learns that better results may be obtained and further 
distances reached by the use of tuning coils, and electrolytic or other 










WIRELESS CIRCUITS. 


267 

sensitive detectors, as well as by high aerials of several wires, where¬ 
upon he aspires to those improvements, and frequently succeeds in ob¬ 
taining them—indeed the up-to-date beginner now usually gets these 
improvements at the start. For the foregoing reasons the employ¬ 
ment of some form of auto or self-restoring detector is assumed in 
what follows herein. 

Reference will now be made to a simple wireless transmitting and 
receiving installation, typical of many successful, but modest ama¬ 
teur stations in operation in this country, a description of which, 
including a complete diagram of the circuits and apparatus therefor, 
together with details of construction of certain apparatus and of the 
aerial, will be given. This station will be assumed to employ a 2-inch 
induction coil and to have a transmitting capacity of, say, 10 miles, 
depending on the length of aerial, etc., and a receiving distance of 50 
to several hundred miles also depending on the length of aerial, the 



sensitiveness of the detector, the location of the station, and other con¬ 
ditions. 

The circuits and apparatus of this station are outlined in Fig. 3, 
in which b may be a 3-cell storage battery, 40 ampere hour capacity, 
giving 6 volts and 5 amperes, which is equal to 30 watts in the pri¬ 
mary circuit p of a 2-inch induction coil i, the dimensions of which 
will be given later. (An Edison copper oxide battery of about 7 bb 
cells may take the place of a storage battery if desired). The watt is 
the unit of electric power, that is, the rate of doing work, and is equal 
tc the product of the volts and amperes of a circuit, the volt being 
the unit of e. M. f., the ampere the unit of current strength. 746 

































2G8 


WIRELESS TELEGRAPHY. 


watts are equal to one mechanical horse power. A kilowatt is 1,000 
watts. The kilowatt is the electrical horse power, k is an ordinary 
telegraph key with extra heavy platinum contacts. (See Fig. 3a.) 
c is a variable condenser in the transmitter oscillation circuit. In 
this case it consists of 6 tubular glass condensers described subse¬ 
quently. tc is the transmitting tuning coil or helix, the dimensions 
of which will be given separately, s g are the spark rods of brass or 
zinc, 3-1G inch by 7 inches; sometimes tipped with brass balls 1 inch 
in diameter in low power stations. Examples of adjustable sjiark 


Fig. Fig. zb. 

gaps are given in Figs. 3 b, 3 c. The spark rods in Fig. 3 b are of zinc; 
those in Fig. 3 c of an alloy. The latter is suitable for handling 250 

watts. These spark gaps 
may be placed in any con¬ 
venient position, but using as 
little wire as possible. Fre¬ 
quently the larger spark gaps 
are enclosed in boxes to dead¬ 
en the sound. In Fig. 3 c the 
upper rod is movable up or 
down by the knob k. It is 
supported on corrugated 
ebonite stands e, screwed to 
a marble base m. The ter¬ 
minals are connected to 
binding screws b V. For a 
2-inch coil a spark gap of one-quarter inch or less should suffice. 

In Fig. 3 also h w is a hot wire ammeter (see Chapter XIV) em¬ 
ployed in nearly all commercial stations and in numerous amateur 
stations for ascertaining the maximum current in the transmitter 
aerial circuit, and hence the best condition of resonance or tuning be- 



Fig. 3c. —Adjustable Spark Gap. 

















269 


HOT WIRE AMMETER. 



tweea the closed oscillation circuit 1, 2, 3, 4, 5, Figs. 3, 4, and the 
aerial circuit, a b tc gc. The hot wire ammeter is frequently con* 
nected between the tuning helix and ground. One form of hot wire 
ammeter as used in prac¬ 
tice is shown in Fig. 3 d. 

This instrument has two 
scales, one reading from 

;o 250 milliamperes, the 
other from 0 to 2,500 
milliamperes. The neces¬ 
sary connections are made 
by means of binding posts 
on the base of instrument. 
gc is a plate glass con¬ 
denser that may be used 
or not in the aerial cir¬ 
cuit. It is found of util¬ 
ity in some cases. It may Fig. zd— Hot Wire Ammeter. 

be constructed of 10 plates, 12 by 14 inches, to */£ inch thick; 
tin foil 10 by 12 inches. 

The receiver tuning coil will be described shortly, v is a variable 
condenser. Some amateur stations use here a fixed condenser, con¬ 
sisting of 2 condensers in series (8 glass plates 4 by 4 inches in each 
condenser; tin foil 3 by 3 inches). In some cases this fixed con¬ 
denser is placed to advantage between contact d' and the earth, vo 
is also a variable receiver air condenser, shown detached from the cir¬ 
cuit, since it may be used or not, as desired; some amateurs, how¬ 
ever, have found it of considerable utility. When this condenser is 
used at v, as just noted, a very small fixed condenser is sometimes 
placed across the terminals of the telephone receiver with good re¬ 
sults. Such an arrangement was used by C. F. Yarley in the early 
days of wire telegraphy to improve rapid signals in a relay. See Fig. 
18. d is a detector of the electrolytic, silicon, carborundum or other 
self-restoring type of detector. Almost every amateur has his favor¬ 
ite detector. Of course a filings coherer or a microphone detector of 
the steel-carbon type (page 162) could be employed. These, how¬ 
ever, are not so sensitive as the other detectors mentioned, and the 
filings coherer has the further disadvantage that it requires in its 
operation a relay, a tapper, or decoherer, with additional battery, etc. 


270 


WIRELESS TELEGRAPHY. 


Also, the rate of signaling by the filings coherer is comparatively 
slow. But, on the other hand, it possesses the important advantage 
that by means of the relay a “call” or alarm bell may be operated. 
For full description of the filings coherer see Chapter IA T , also con¬ 
sult Index. For information concerning the silicon and other auto 
detectors see Chapter XIV. 

Fig. 4 is very similar to Fig. 3, except that some of the instruments 
are shown in Fig. 4 somewhat as they appear in practice. For in¬ 
stance, the spark gap sg is shown within the tuning helix tc. Also 
double pole, double throw switch sw is shown in Fig. 4 and separate y 



Fig. 4.—Wireless Circuits with Throw Over Switch." 


in Fig. 3. By means of this switch the transmitter and the receiver 
circuits may readily be alternately connected to the aerial wire at the 1 
will of the operator. When the switch is up it is set for sending, and 
vice versa. This switch may be of the knife edge double throw type, 
as indicated in the figure, or of the button type shown at right top 
corner of figure. In the latter the strips are pivoted at the center 
and are movable jointly to the right or left by a knob on the in¬ 
sulated cross piece cp. When turned to the left the aerial is con¬ 
nected to the transmitter side; when to the right, to the receiver 
circuits. The circuits may be traced by means of the small letters 
and figures in each cut; a, b, c; 1, 2, 3, etc. Similar letters refer to 
corresponding apparatus in both figures. 

It may be noted that the arrangement of circuits shown in Figs. 
3, 4 is merely suggestive; many variations thereof are possible and 
are in actual operation, ht in Figs. 3, 4 represents a pair of head 
telephone receivers, watch case type, illustrated separately in Fig. 5. 






































WIRELESS APPARATUS. 


271 


WIRELESS TELEGRAPH APPARATUS. 

Head Telephone* Receivers.— In the cut, Fig. 5, the ear piece is re¬ 
moved in one receiver to display the interior construction thereof. 
When high sensitiveness is desired 
each receiver is wound to 1,000 
ohms with No. 40 or 50 copper wire. 

The arrangement and adjustment 
of the head bands are self-explana¬ 
tory. As indicating the sensitive¬ 
ness of such receivers it may be 
noted that when the tips of the 
cords are moistened and then placed 
in contact a sound is heard in the 
receivers. The e. m. f. and current 
thus developed probably do not ex¬ 
ceed the one-hundred-thousandth of 
a volt and the one-millionth of an 
ampere. 

Potentiometer. — This instrument is indicated by p' in Figs. 3, 4. 
It is a device for varying the potential at the terminals of the dry 
cells b of the detector circuit, by means of a resistance and a sliding 
contact sc. This effects a useful purpose inasmuch as detectors of 
the electrolytic type and certain others operate most efficiently at a 
critical potential or pressure at their terminals, which point is at¬ 
tained by the potentiometer. The operation of this device is based 
on the fact that electric potential falls in a circuit in proportion to 
the resistance overcome. Thus in Fig. 6, let w represent a high re¬ 
sistance wire or rod across the thick wire t t', of a 1 volt battery b. 
The electromotive force in this w T ire will fall uniformly from 1 volt 
positive at 1, to zero at 0. Hence, if the resistance of w is, say, 100 
ohms, and a scale representing 100 ohms is placed along its length, in 
divisions of, say, one ohm, the voltage at any point may easily be 
calculated. Thus, if the sliding contact c is placed at 20 ohms on 
the scale, where the potential has fallen .20 of one volt, the e. m. f. 

271 








272 


WIRELESS TELEGRAPHY. 


at the detector d will be .80 volt, minus the drop in potential due to 
the resistance of the leading wire w'. Obviously the potential at d 
may be varied up and down in very minute gradations by moving the 
sliding contact along the potentiometer resistance u> until the best 
working potential or current for the detector is found. 

Some potentiometers for wireless telegraphy are made in rheostat 
form with very small variations of resistance between steps. Others 
are made of high resistance alloys in a continuous length. In some 




Fig. 7.—Carbon Potentiometer. 


potentiometers of this type the resistance is 800 ohms. In another 
simple and efficient form of potentiometer due to Gernsback and illus¬ 
trated in Fig. 7, a graphite rod, l l / 2 inches long, */g inch wide, is em¬ 
ployed as the resistance. Two rods are supplied with this device, one 
of 300 ohms, the other of 500 ohms. The rods are held in a groove 
in the base by two clips and are interchangeable with one another. 
Ordinarily not more than 100 ohms are required in practice. Four 
dry cells are used with this device. To prevent wear and tear on the 
graphite rods, the slider is provided with a roller ball contact. The 
two end binding posts are in contact with the ends of the graphite 
rod. The battery wires are connected to these posts also; a telephone 
receiver terminal is connected with the right hand post and a wire 
leads to a terminal on detector d, virtually as outlined in Fig. 6. 

Condensers, Notes on, etc.— A type of variable condenser for the 
transmitter oscillation circuit in considerable use in low power ama¬ 
teur stations is illustrated in Fig. 8. This consists of 6 tubular glass 
condensers 1 inch by 6 inches, half covered with tin foil or aluminum 
foil. These tubes are arranged in a rack for easy removal and adjust¬ 
ment or tuning. The receptacle for each tube has a circular recess 
and spring clip at the top and a round metal knob at the bottom, 
whereby the tubes may be quickly snapped in or out of service; they 













CONDENSERS. 


.) W Q 

£ i O 


are connected in multiple series as desired; the upper terminals being 
connected together by a metal strip. 

Leyden jars and glass plates are also largely used to provide ca¬ 
pacity for the transmitter oscillation circuit. Leyden jars for this 
purpose are obtainable from electro-theraupeutic and other electrical 
supply houses. Two or three 4-quart jars will suffice for a 2 or 3-ineh 
induction coil. These may be connected into the circuit at will by 
two or three 2-point switches. A simple form of variable receiver 
condenser is shown in Fig. 9. It consists of 5 fixed and 4 movable 
plates, inch thick, separated by air. The fixed plates are soldered 
together at one end; likewise the movable plates. The latter slide in 
grooves *4 inch deep and iV inch apart and are movable to and 
from the fixed plates by an insulated handle h. The maximum ea- 



Fig. 8.— Condensers —Fig. g. 


pacity of the condenser is obtained when the movable plates are 
pushed all the way in, and vice versa. This condenser is 1014 inches 
long by 6 >4 inches high, by 2p4 inches wide. Weight 3 pounds. An¬ 
other type of variable receiver condenser is described on page 202 and 
illustrated in Chapter XIV. 

Glass plate condensers suitable for the transmitter oscillation cir¬ 
cuits may be constructed as follows. The plates may be 10 bv 10 
inches square or other desired size. The glass should be first 
thoroughly cleansed with a solution of ammonia and water. 

Shellac the glass thoroughly on both sides and edges. Cover with 
tin foil to within 2 inches of the edges on both sides of plate, round¬ 
ing off the corners of the foil. The foil is laid on the plate by a brush 
well wetted with shellac or banana oil, care being taken to avoid 
blistering due to the ingress of air or a surplus of oil or shellac be¬ 
tween the foil and glass. This work must be done very carefully. To> 
connect these plates lay, for instance, 6 or 8 of them in a row on a 






































274 


WIRELESS TELEGRAPHY. 


table. Call the side presented to the observer a, and continue a strip 
of foil down to the right hand lower corner and just around the edge 
of each plate. Now turn the plates over and repeat the same opera¬ 
tion on this face b of the plate. Then procure a suitable wooden 
frame, well coated with shellac, with grooves or racks one-quarter 
inch deep, into which these plates can slide edgewise (somewhat as 
indicated in Fig. 9). Place a metal strip along the front and back of 
the floor of the rack so that when a plate is placed vertically in a 
groove, face a will be in contact with the front strip and face b with 
the back strip. The front and back strips are then connected in the 
primary oscillation circuit. To vary the capacity more or less plates 
may be inserted in the rack, or a plate may be tilted on its edge to 
break contact with strip. It will be understood that placing 2 equal 
condensers in series or tandem reduces the total or resulting capacity 
to one-half that of a single condenser, 3 equal condensers in series 
reduces the total capacity to one-third of a single equal condenser, 
etc., while placing 2 or 3 condensers of equal capacity in parallel or 
multiple (that is, abreast, so to speak) doubles or trebles the total 
capacity. Condensers are shown in multiple, in series of 2 at c Fig. 
4. When condensers are placed in series with the aerial wire, the 
total capacity of the aerial is diminished and consequently the wave 
length is shortened. This may be compensated by adding inductance 
or a greater length of wire in the aerial, but capacity is not usually 
inserted in the aerial except to shorten the aerial or, rather, the wave 
length. For reference to other types of condensers see Index. 

Induction Coil. —Briefly described, a 2-inch induction coil i, Fig. 
10, may consist of the followng parts. An iron core ic, 9 inches long 
and 1 inch in diameter, composed of a bundle of very soft No. 14 iron 
B and S wires. The primary coil p may consist of 2, or, at most, 3 
layers of No. 14 insulated copper wire, wound over the iron core, but 
separated therefrom by a layer of paraffin paper. The primary coil 
should not take up over 8 inches of the core, leaving about half an 
inch clear at each end. A hard rubber tube t is brought over the full 
length of the core and primary coil. Hard rubber rings or flanges 
r, r, are placed vertically over the tube snugly, about half an inch 
from each end, to serve as the end Avails of the secondary coil. The 
secondary coil is composed of No. 36 double silk-covered copper wire. 
About 2*4 pounds of this wire may be used for the secondary coil. 
About 125 turns of this wire will cover one inch of the surface of the 


INDUCTION COILS. 


275 


tube, lengthwise. There are 13,283 feet to the pound of this wire; its 
resistance is .43 ohms per foot, or 5,715 ohms per pound. From this 
data the external dimensions of the coil may be calculated; the outside 
diameter of the flanges will be about 3^2 inches. 

For 6-inch coil, No. 12 insulated copper wire should be used for 
the primary coil, with a core 12 inches long and 1*4 inch in diameter. 
For the secondary of a 6-inch coil about 9 pounds of No. 36 double 
silk-covered copper wire would be required. 

It is the usual practice in constructing these coils to wind the 
secondary coil in sections of, say, one inch each for the purpose of 
improving the insulation. Each 
section is separated by thick paraf¬ 
fin paper rings r' slipped over the 
rubber tube. In joining up the 
respective coils to one another it 
is advisable to connect the outer 
terminals of adjoining sections to¬ 
gether in one case and the inner 
terminals in the next case. Thus, 
if there are four sections, let the 
inner terminals of 1 and 2 be joined, the outer terminals of 2 and 
3, the inner terminals of 3 and 4. The outer terminals of 1 and 4 
would then constitute the external terminals of the coil. Great care 
should be taken to insulate the windings of the secondary coil 
thoroughly by running the wire through hot liquid paraffin just prior 
to winding and by pouring the liquid over and around the coil after 
winding, to fill in the spaces. 

When the coil is completed it is fixed on a well-shellacked wooden 
base, or a base of hard rubber. An interrupter i consisting of a strip 
of spring steel s carrying a small piece of iron as an armature is 
attached to the base in such manner that the armature comes opposite 
one end of the core ic. The strip is also supplied with a platinum 
contact n, opposite an adjustable contact n' suitably supported from 
the base. The spark condenser is often placed in a hollow space be¬ 
neath the base. This condenser usually consists of strips of tin foil 
separated by thin paraffin paper, free from pin holes or other de¬ 
fects, the alternate sheets of the foil being connected together at their 
respective ends, as indicated in the figure at c. Experiment will 
probably be necessary to determine the proper number of sheets of 
tin foil to employ for best results. About 100 sheets, 7 inches by 5 



Fig. io. 

























276 WIRELESS TELEGRAPHY. 

inches, may suffice. The number of sheets should be increased or de¬ 
creased until the spark at the contacts of the interrupter is practically 
eliminated. In case of inability to eliminate the spark look well to 
the insulation of the condenser, for punctures. Key k and battery b 
complete the primar} r circuit. For more complete details of construc¬ 
tion than is contained in the foregoing the reader may be referred to 
any one of a number of books exclusively dealing with the subject of 
induction coils. 

Power Transformers. — In amateur stations where alternating cur¬ 
rent of, say, 110 or 220 volts and 60 or 125 cycles is available a small 
transformer (without interrupter) may be utilized in place of the 
induction coil, and usually with more satisfactory results. Small 

transformers suitable for such service are now available at a moderate 
outlay. An example of this type of transformer is given in the ac¬ 
companying illustration, Fig. 11. This is a closed core transformer. 
The primary coil is provided with a switch s , whereby it may be 

tapped at four different points, giving 4 variations of output. This 

transformer is so constructed as to give resonance between the pri¬ 

mary and secondary 
circuits when a con¬ 
denser of suitable ca¬ 
pacity is employed in 
the secondary circuit, 
thereby permitting 
the spark discharges 
to be varied in the 
manner mentioned in 
connection with res¬ 
onance transformers, 
Chapter XIY. The 
core c of this trans¬ 
former is made up of laminated strips of soft iron formed into a con¬ 
tinuous oblong frame, over the ends of which the primary and sec¬ 
ondary coils p, s' are respectively wound. 

An induction coil may be introduced into a 110 volt alternating 

..... o 

circuit with a suitable resistance in the primary to regulate the cur¬ 
rent; or a 110 or 220 volt alternating current may be changed to a 
direct current for an induction coil and interrupter by means of a 
current rectifier. 





TUNING COIL. 


277 


Transmitter Tuning Coil. —A transmitter tuning coil of the auto 
transformer type that may be constructed by an apt amateur and that 
is suitable for a 2-inch experimental set is outlined in Figs. 12, 13, 
after plans detailed by Mr. A. C. Austin in “Modern Electrics,” Yol. 
1, to which valuable magazine the present writer is indebted for a 
number of cuts and practical suggestions used herein. The dimen¬ 
sions of the frame are as follows: A base of hard wood b 1 inch thick 
and 17 l / 2 inches long by 9 inches wide, with edges rounded off. On 
this is placed the frame proper consisting of two hard wood discs d 
11 y 2 inches in diameter, *4 inch thick. In cutting the circles a base 
3 y 2 inches wide at bottom and % inch high is left as a stand for the 
frame, as outlined at b, Fig. 12, which is an end view of the frame. 
In the center of the discs a hole h iy inch in diameter is bored for 



Fig. 12. 



\Z3 <f 


Fig. 13. 


the passage of the spark rods r, h. The discs are held apart by eight 
strips of hard wood 10 inches long, iy 2 inch wide, inch thick, the 
ends of which strips are screwed on to the inner sides of the discs 
flush with the circumferences thereof, as indicated; the narrow side 
of the strips outwards. A double binding post p is screwed firmly 
on to the top of each disc, a flattened surface being prepared therefor. 

The coil proper may now be placed on the frame. For this pur¬ 
pose about 35 feet of "No. 8 B and S bare copper wire are used. To 
prepare for the winding a small hole is first made in the top strip 
s'. Fig. 12, and beginning at a point % inch from the inner side of 
the disc d, a small slanting groove is made crosswise on the top strip 
in the direction in which the wire will run. The frame is then 
turned towards the observer and a groove is made in the next cross 
strip, 34 inch from the disc, and so on, so that when a revolution of 
the frame is made the next groove on the top strip will be one inch 
from the disc. This process is continued across to disc d', when it 




















278 


WIRELESS TELEGRAPHY. 


will be found that there are spaces'for 10 turns of the wire. The 
wire is now inserted in the small hole on the top strip from below, 
and is attached to the left binding post p. The wire is then wound 
snugly over the strips, following the route of the slanting grooves, 
and is connected to the right hand binding post p in the same man¬ 
ner as at the beginning. The sliding contacts are made by slotting 
the ends of 2 binding posts down to the first screw hole, by means 
of which the binding posts, as at 2, 3, may be attached to any de¬ 
sired part of the tuning coil. 

Two hard rubber rods n n', 6*4 inches in length and ^4 in diameter 
are screwed on to the base from below. A rubber strip is screwed 
on to the top of each rod, and a double binding post p' is bolted to this 
strip. For the spark rods, or tips, 2 brass rods 7 inches long are em¬ 
ployed. A rubber handle l 5J4 inches long and ^4 inch in diameter 
is screwed on to one end of each rod. Each rod is passed through one 
of the apertures in the double binding posts p'. Brass balls, 1 inch in 
diameter, or of any other desired size, may then be screwed on to the 
other end of the brass rods. The balls may now be passed through the 
central hole in each disc and placed in position, as outlined in the 
figure. The spark gap is'then ready for adjustment, as required. To 
raise the base of the coil from the table a rubber foot f may be 
screwed on to each corner of the board. 

Referring to Fig. 4, the corresponding connections on the tuning 
coil, Fig. 13, may now be indicated. Wire x goes to one terminal 
of the secondary coil s; x' goes to the other terminal of s. Wire m 
goes to the sliding contact 2; wire m' goes to sliding contact 3. Wires 
t and V respectively go to the terminals of condenser c. Wire e goes 
to a terminal of condenser go. 

A good quality of flexible rubber insulated wire should be used for 
the wires leading from these high potential circuits; and no more 
wire than is necessary to properly make connections should be em¬ 
ployed, thereby to minimize induction and resistance. A cable con¬ 
siderably used for this work has a stranded copper conductor equal 
to No. 18 B and S, coated with several layers of rubber insulation. 

Transmitter Oscillation Transformer.— Fig. 14 typifies a form of 
variable oscillation transformer of the Tesla coil type that may be 
connected up in the place of the transmitter tuning coil, Fig. 4, where 
loose coupling is desired. In this device the primary coil p, placed on 
one end of the frame r, consists of a copper strip one inch wide 


OSCILLATION TRANSFORMER. 


279 


arranged in a spiral of 5 turns, more or less of which may be added 
to or deducted from the circuit by the rotary contact c. This con¬ 
tact does not at any time leave the ribbon, the play between spirals 
being taken up at the shaft m } on which the contact arm is carried. 
The secondary coil s, seen between the ends of the frame, is composed 
of 41 turns of thin copper ribbon ]/% inch wide, y 1 ^ inch apart, the 
number of which turns in circuit may be increased or decreased by 
the sliding contact c'. 

Inasmuch as high frequency currents travel mostly on the surface 
of a conductor, not having time to penetrate to the interior (a phe¬ 
nomenon known as 
the “skin” effect) the 
use of metal strip in 
high frequency work 
is an advantage, since 
it affords a larger 
surface and therefore 
a larger current car¬ 
rying capacity than 
would a wire con¬ 
ductor of the same 
weight. This type of 
oscillation transform¬ 
er is made to operate 
on outputs ranging Fig. 14. — Transmitter Oscillation Transformers. 
from 250 watts to 1 

kilowatt. The size of the smaller instrument is 8 by 8 by 11 inches. 
This oscillator will give a maximum wave length of 600 meters, 
which with inductance in series may be increased to 900 meters. It 
may be noted here that the inductance of a spiral or helix of wire 
may be calculated approximately by the formula l = 3.1416 x d X 
n)* X l, in which d is the mean diameter in centimeters of one circu¬ 
lar turn of the helix, n is the number of turns per centimeter and l 
is the length of the helix in centimeters. The answer is in centi¬ 
meters. To get the answer in microhenrys divide the result by 1,000. 

Receiver Tuning Coil. — A type of tuning coil that has been largely 
used in commercial work is shown in Chapter XIV, Fig. 14. A 
somewhat simpler form may be constructed practically as follows: 
Procure a fibre or w r ooden tube or roller inches long; diameter 






280 


WIRELESS TELEGRAPHY. 


2J4 inches. Thoroughly shellac the same and wind closely with 
about 300 turns of No. 24 enameled or single silk-covered copper 
wire, securing the ends by means of a broad-headed tack and leaving 
a few inches of surplus wire at each end. Leave about inch of the 
tube uncovered at each end. Get two pieces of hard wood 3^2 inches 
square and ^4 inch thick, and attach to each end of the tube, and pass 
the terminals of the coil through a hole in the wooden ends and 
attach the terminals to a binding post, as shown in Fig. 15. Now re¬ 
move a strip of enamel, or silk, as the case may be, ^4 inch wide and 

extending across the top 
of the coil its full length, 
leaving the bare copper 
wire exposed. Two brass 
pieces inches long and 
% inch square are placed 
side by side, but not touch¬ 
ing, over the bare strip. 
These are connected by a 
screw to the framework of the coil. A binding post is connected to 
each of the brass rods. Two sliding contacts are placed in position 

on each rod. The slid¬ 
ing contacts shown in 
the figure are provided 
at their lower ends with 
a roller ball bearing 
which is held snugly 
against the bare wire by 
a spiral bearing spring 
not shown. These con¬ 
tacts are arranged so 
that the ball can only 
touch one turn of the 
coil at a time, and the 
roller bearing avoids in- 
Fig. i6 . jury to the coil. If used 

in connection with the circuits shown in Fig. 3, wire V might be 
brought to the lower left hand binding post, the lower right hand 
post would be idle. Wires c' and cV would be connected with the two 
upper, or sliding contact posts respectively. The sliding contacts are 
movable along the coil by means of the small insulated knobs shown. 














































































WIRELESS RECEIVING SET. 


281 


Another form of receiver tuning coil employing but one sliding 
contact is shown in Fig. 16. This coil is wound on a fibre tube and 
consists of 200 turns of No. 30 bare copper wire, the adjoining turns 
of wire not touching. The sliding contact is so arranged that it 
touches only one turn of the coil at a time. With an aerial 60 to 80 
feet in length wave lengths of 1,500 meters may be received with this 
coil. When a receiver tuning coil with one sliding contact is em¬ 
ployed, the circuit connections may be identical with those shown in 
Fig. 3, but with slider d' omitted. The inductance of this tuning 
coil is 700 microhenrys. The length of the coil is 4^4 inches, diame¬ 
ter 5 inches. 

A receiving oscillation transformer is shown in Fig. 17. This con¬ 
sists of two coils, one sliding within the other, as indicated, to vary 



Fig. i7.—Receiver Oscillation Transformer. Fig. i8. 

the degree of coupling. Each coil is provided with a sliding con¬ 
tact, whereby the number of turns and consequently the inductance 
may be varied as desired. These coils are wound practically as de¬ 
scribed in connection with the previous figure. The length of coils 
is 4 y 2 inches; diameter of larger coil 5 inches, of smaller coil 4]/ 2 
inches. Number of turns of wire on each coil 200, No. 30 copper 
wire. In Fig. 17 are also indicated a “ferron” detector, a variable 
condenser, a fixed condenser and small switch, comprising a compact 
and practical wireless receiver set. The knob of the variable con¬ 
denser is seen at the right, on the top of case; the switch on the mid¬ 
dle of cover, the fixed condenser on the side, and the detector at the 
left of cover. This detector is of the contact, mineral type. The 


















282 


WIRELESS TELEGRAPHY. 


active mineral element is contained in a small cup. Contact with 
this mineral is made by a vertical pointed wire or rod, and the de¬ 
gree of pressure is regulated by flat springs adjustable by screws, as 
in the case of the silicon and carborundum detectors. 

Variometers.— For experimental work inexpensive variometers are 
now coming into use for tuning the receiving circuits. The spherical 
spools are made of hard seasoned wood and solid wire (not stranded). 
Otherwise they resemble the variometer illustrated in Chapter XIV. 
An arrangement of the variometer in a reciving circuit is shown in 
Fig. 18, in which a is the aerial, v is the variometer, r is the pri¬ 
mary of receiving oscillation transformer rt. c is a variable con¬ 
denser. fc is a small fixed condenser and t is a head telephone re¬ 
ceiver. If desired the variometer can be inserted in the circuit of the 
secondary coil, or for still more accurate tuning a variometer can be 
placed in the aerial and in the secondary circuit. As previously 
noted, the use of variometers eliminates the defects of possible im¬ 
perfect contacts of sliding coils and gives a more continuous adjust¬ 
ment than is obtainable otherwise. 


Wave Meters.— A wave meter is a very desirable adjunct to the 
outfit of a wireless station, inasmuch as by its use the wave length of 



* Fig. 19. Fig. 20. Fig. 21. Fig. 22. 


outgoing and incoming waves may be readily ascertained. These in¬ 
struments, capable of measuring wave lengths of from 350 to 1,500 
meters, are now procurable for experimental purposes at a reasonable 
cost. Such wave meters m in the following figures comprise a fixed 
inductance l and a variable capacity vc, with an index pointer or 
finger p (see page 312) ; the ordinary detector d and head telephone 
receiver t being utilized to determine when tuning between the aerial 
and wave meter circuits is obtained. To measure the length of out- 





















WAVE METERS. 


283 


going waves the apparatus is arranged as indicated in Fig. 19. The 
inductance coil l is placed near to the auto transformer l of the 
transmitter circuit, a c s, and the variable condenser vc is adjusted 
until the maximum sound is heard in the head telephone t, at which 
time the pointer p will be opposite a certain figure on the scale. A 
table accompanies the meter showing the wave length for this figure 
in meters. Two separate inductance coils lV, Fig. 22, are furnished 
with the meter for long and short wave lengths, and for each coil a 
separate table is provided. For measuring incoming waves the ar¬ 
rangements shown in Fig. 20 may be employed, in which the in¬ 
ductance ring or coil l is placed adjacent to the receiver coil rc, and 
the adjustment and calculation is made as before. The meter may 
be and in practice frequently is connected regularly in the receiving 
aerial circuit, as outlined in Fig. 21, and has been found of advan¬ 
tage in eliminating interference from other stations. The meter as 
a whole is outlined in Fig. 22. The variable condenser is contained 
in a box m, on the cover of which is placed the index finger p and 
scale, and knob k for turning the movable plates of the condenser and 
the said index finger. The terminals of the inductance coil, the de¬ 
tector and head telephones are connected to binding posts on the box. 
The wave meter is calibrated at the laboratory with either one or 
other of the more sensitive detectors and with the usual head tele¬ 
phones in the circuit. Hence, the wave meter will give closely ac¬ 
curate measurements of the wave lengths when used with either the 
perikon, silicon or carborundum detectors, or with any of the standard 
head telephones, as the capacity of these instruments is practically 
the same. In the use of wave meters the meter coil should not be 
brought closer than one inch to the coil under test, as otherwise the 
inductive reaction of the meter coil upon the other may give you in¬ 
accurate readings. 


AERIALS. 

For the general purpose of amateurs a mast or flagstaff 30 to 50 
feet high is ample. A 30-foot mast may be placed on the top of a 
building by suitable construction, or an adjoining chimney or tree 
may be utilized to serve as a support for the aerial, instances of which 
will be given presently. As far as possible a place should be selected! 
for the aerial where it will not be shut in by high iron frame build¬ 
ings, trees, etc., as these absorb or screen the energy of transmitted 
and incoming waves. 



284 


WIRELESS TELEGRAPH'?. 


In some cases small iron pipes have been used successfully to form 
a mast for the aerials. For this purpose three lengths of 20-foot 
iron pipe 3 inches, 2 ]/ 2 inches, and 2 inches in diameter, respectively, 
may be employed, with screw threads at each end and the necessary 
reducer couplings. The first two lengths of pipe, after being pointed 
end to end, may be raised by means of a block and tackle fastened to 
the top of a vertical wooden post (provided with an iron collar 
through which the pipe is raised) and to the bottom of the pipe, the 
mast being steadied in raising by guy wires attached to the top wire. 
A third pipe is then jointed to the second and raised and steadied as 
before. If a fourth or fifth pipe is desired a second set of guy wires 
will be advisable. The guy wires should be insulated in sections by 
porcelain or other “split circuit” insulators. (See b c, Fig. 28.) Es- 
jiecially if used for transmission the iron mast should be well in¬ 
sulated from the earth by, for instance, placing its base in a wooden 
socket embedded in cement. A cap or petticoat should be placed at 
the base to shed the rain water. Before raising the pipe or any other 
form of wireless mast an insulated pulley with halyards whereby to 
raise and lower the aerial should be attached to the pipe or masthead. 

Assuming that the necessary support for the aerials has been pro¬ 
cured, the number of wires to be erected is to be considered. One, 
two or more wires may be used, and six and eight wires are some¬ 
times used in the aerial of amateur wireless stations. Fair results are 
obtained with one fairly high wire in connection with tuning coils 
and sensitive detectors, but the experience of numerous experimenters 
has shown that all things considered a 4-wire antenna is usually the 
more satisfactory. The 4-wire antenna is preferably connected up so 
that it may be used as a straight or as a looped aerial. Some ex¬ 
perimenters have found that the looped aerial obviates largely the 
interfering effects of atmospheric static, or x’s, by providing a by 
pass, so to speak, through the tuning coil l, as in Fig. 24. Others 
have found that it obviates induction from neighboring electric light 
and power wires. De Forest, who patented the looped aerial, claims 
that as it is in a sense a closed oscillation circuit it is better adapted 
for receiving than a straight aerial, since the closed circuit tends to 
prolong the oscillations, it being a poor radiator of energy. A pos¬ 
sible disadvantage of the looped aerial for small power stations is in 
the use of the anchor gap, shown in Figs. 23, 24, which is employed 
to minimize switching, and which may reduce the transmitted energy. 


AERIALS. 


285 


Frequently two tuning coils are used with the looped aerial, as shown 
in Fig. 98a of the Shoemaker system. 

Still other experimenters find that the arrangement of double 
sliders, shown in Fig. 3, for instance, .affords a side path for static 
discharges to earth through the coil rc, contact d' and wire f. This 
plan obviates the use of an anchor gap arrangement in connection 
with the looped aerial and avoids any loss of energy that may occur at 
that point. Of course, however, switches could be provided to dis¬ 
place the anchor gap in the looped aerial if the loss of energy due 
thereto should warrant it. 

As atmospheric static discharge currents are usually of a continu¬ 
ous or direct nature (not alternating), an inductance coil is not a 
barrier to them, while a condenser is. On the other hand, inductance 
coils oppose the passage of high frequency alternating currents, while 
condensers do not. 

The nature of the material composing the aerial wires is not im- * 
portant (excepting iron wire owing to its magnetic effects), provided 
the wire possesses sufficient strength to withstand the strain of wind 
storms. No. 14 B and S soft or hard drawn copper, stranded phosphor- 
bronze or aluminum wire are now much used for aerials; aluminum 
especially, owing to its combined lightness, strength and durability. 
Galvanized iron wire may be used. 

In many instances amateurs do not possess transmitting apparatus, 
contenting themselves with a means of catching passing aerial signals. 
This of course much simplifies the station. If the station is used for 
transmitting, the insulation of the aerial and of the leading in wires 
requires much more careful attention than if only used for receiving. 
The higher the power employed, also, the greater is the need for care 
in insulating the aerial at all points, as otherwise the energy of the 
waves will be uselessly diverted or absorbed. 

An arrangement of a 4-wire aerial for transmitting and receiving 
is outlined in Fig. 24. The vertical wires w w are suspended between 
two hard wood spreaders w w. These spreaders may be 2> l / 2 inches 
wide, 1 inch thick and, to allow a spread of at least iy 2 feet between 
the wares, 7 feet long. Or wooden spars about 2 inches in diameter 
and 7 feet long, and shellacked for protection against the weather, 
may be utilized in light installations. To insure ample insulation for 
the aerial the spreaders w w are upheld at top and bottom by rod 
insulators, two types of which are shown, c c are corrugated composi- 


286 


WIRELESS TELEGRAPHY. 


tion insulators; p p may be rubber or porcelain rods, each 6, 8, 10 
inches or more in length and about 1 inch in diameter. These rods 
are connected or tied to one another and to the spreaders by a wire 
through eyes at each end. To obtain higher insulation if desired more 
rods c or p may be connected in tandem. Or, on the other hand, in 
some cases only one rod at each end of the spreaders may be necessary. 
For a two-inch coil one rod 6 inches long should be ample. To fasten 
the wires to the spreaders, strain insulators like those shown at d e, 
Fig. 28, may be utilized, or holes may be bored in the wood for bush¬ 
ings of porcelain, rubber or other insulating material, and through 



which the wires are passed and held by a knot in the wire, through 
which a nail of the same material may be drawn to prevent the wire 
from slipping out. In Fig.'24 the aerial is attached at a to the top 
of a mast, a chimney or other suitable support. The lower end is 
held securely by a guy wire or rope (not shown) at a'. The leading 
in wires w' w' are brought into the operating room through bush¬ 
ings b b of porcelain or other insulating material. Where the wires 
pass through the bushing a good quality of rubber insulated cable 
should be used, in which case one bushing will suffice for the leading 
in wires. To avoid cutting through a wall, a board may be fastened 
across the top of a window above the sash, or a round hole may be 
cut in the glass, through which the wires may be led into the instru¬ 
ment room. The vertical wires w w are all securely connected to¬ 
gether by cross wires of their own material at n, and for the looped 





















































HOUSETOP AERIALS. 


287 


aerial in pairs at n', as shown. Where the looped aerial is not em¬ 
ployed the wires may be bunched at a' and thence be brought jointly 
into the operating room. Straight away aerials, that is, not looped, 
are indicated in Figs. 26, 27. In Fig. 24 the receiving apparatus is 
outlined at the left, showing the arrangements for a looped aerial cir¬ 
cuit. An anchor gap a leads to the transmitting apparatus. An 
adjustable anchor gap is shown separately in Fig. 23, where a is the 
aerial, r is the receiver and t the transmitter wires. Cut out switches 
are not shown in this figure. If it is desired to utilize the arrange¬ 
ment, Fig. 24, as a t or sloping aerial, the end a' may be connected to 
another house, chimney or mast, in which case the leading in wires 
w' w' would be connected at x x. 

A simpler plan of securing the aerial to a mast, house, etc., at a 
is shown in Fig. 25. In this plan 2 porcelain or rubber tubes or 
bushings, 12 or 14 inches long, are tied side by side by strong cord r. 
A rope passing through tube p' is attached at a to the mast; a similar 
rope passing through the tube p upholds the spreader w and the 
wires w w. 

In Fig. 26 a method of suspending a single wire aerial from a 
neighboring chimney c, from which it is insulated by a rod insulator 
p and led down to a bracket insulator b on the side of the house to 
the operating room through a bushing b. 

One way of employing a 25 or 30-foot mast m on a housetop is in¬ 
dicated in Fig. 27. The plan of suspension outlined in Fig. 25 might 
be utilized here. The aerial is drawn away from the mast by a rope 
and pulley p attached to the lower spreader a'; the wires are then 
led to a glass insulator g, from which they pass to the operating room. 

Where an aerial is employed solely for receiving, high insulation, as 
already intimated, is not essential. To fasten the wires to the 
spreader in this case insulated screw eyes f, as shown in Fig. 28, or 
ordinary screw eyes covered with insulated tape, may be utilized, and 
the upper spreader may be fastened to its support by a rope direct or 
by means of the device shown in Fig. 25 at r. 

In Fig. 28, a is a porcelain or composition tube or bushing. These 
are made in various lengths, b c are porcelain guy wire or split 
circuit insulators, d and e are “giant” and “globe” strain insulators. 
f is a wood screw eye insulator, insulated by a rubber sleeve r. 

In order to facilitate repairs to the aerial, or to avoid storms, pro¬ 
vision can be made for raising and lowering it by means of a pulley 


288 


WIRELESS TELEGRAPHY. 


at the masthead, and halyards. The wires of the aerial should be 
kept as far removed as practicable from iron walls, tin rools, etc., 
especially for transmitting, as these materials tend to screen or to 
short circuit the electric waves by a condenser effect. The wires of 
the aerial should be at least 18 inches apart in amateur installations. 
Adding more wires in parallel in the aerial does not materially aftect 
the wave length except in so far as this may vary the capacity and 



Fig. 28.—Insulators. 


inductance of the aerial. The nature of the ground for the aerial in 
wireless telegraphy is of much importance. Wherever possible a 
water pipe should be selected, not a gas pipe, as the latter is fre¬ 
quently insulated more or less at joints, thereby introducing high 
resistance into the circuit. If water pipes are not available connec¬ 
tion should be made with a metal plate or rod embedded in moist 
earth. 


GENERAL NOTES ON TUNING, ADJUSTMENT OF APPARATUS, ETC. 

When two amateur or other stations desire to attune their ap¬ 
paratus for the interchange of signals, it is first advisable that they 
adjust their aerials and apparatus as nearly as may be to a corre¬ 
sponding wave length. In the absence of a wave meter the wave 
length of an aerial may, as previously stated, be estimated as ap¬ 
proximately four times the length of the aerial. This refers to the 

























ADJUSTING DETECTORS. 


289 


distance from the far end of the aerial to the instruments. The dis¬ 
tance from the instruments to ground should be short. An agreed- 
upon signal should then be transmitted by one of the stations at inter¬ 
vals of 20 or 30 seconds, the receiving operator in the meantime 
varying the position of the receiving tuning coil and variable con¬ 
denser until best signals are obtained. In lieu of a wave meter or hot 
wire meter an incandescent lamp may be placed in the aerial to in¬ 
dicate by the degree of brightness of the filament the best point of 
resonance or tuning. Also the sliding contact may be moved up and 
down over the helix, or tuning coil, but not touching it, and the point 
of longest spark noted. This will be the point to place the sliding 
contact. An adjustable anchor gap may also be used for this pur¬ 
pose. 

To “listen in” or to adjust for incoming signals the connections in 
Fig. 3 may be employed. If desired the tuning coil rt may be used 
as a single sliding contact device by placing contact 2 at the lower end 
of coil or by disconnecting it and using the upper contact only. If 
no signals are heard the sliding contact c' of the coil may be moved 
along the slide 10 or 12 turns at a time, pausing at each step for sig¬ 
nals, meanwhile varying the condenser c gradually. If after going 
up and down the coil once or twice without getting signals it will be 
advisable to examine all connections carefully for imperfect contacts. 
Sometimes the detector is at fault. To determine this point the use 
of a buzzer, as described on pages 61, 155, placed 6 or 8 feet away, 
may be resorted to. If the detector is in proper order it will promptly 
respond to the waves set up by the buzzer. In adjusting the elec¬ 
trolytic detector the following procedure has been found successful. 
By means of the adjusting screw depress the Woolaston wire into the 
solution (4 parts water to 1 part nitric acid) until a boiling sound is 
heard in the telephone. Then raise the wire until a hissing sound is 
heard and continue to raise it until the sound is at its loudest. Then 
adjust the potentiometer until the sound disappears. The buzzer 
should be operated at frequent intervals to insure that the detector 
connections are intact; it is not uncommon for the fine wire to rise 
out of the liquid due to jarring of the table. Many amateurs get 
along very well, however, without the aid of a buzzer, especially after 
they have become adepts at tuning, but it unfrequently saves time in 
showing that the detector and not the tuning is at fault. Opening a 
nearby electric light switch will effect the same result by causing a 


290 


WIRELESS TELEGRAPHY. 


click in the telephone if the detector is in order. When the receiving' 
apparatus is at its best point of syntony or tuning the received sig¬ 
nals come in clearly and regularly. 

Some amateurs have found that the point of best contact in the car¬ 
borundum detector is between the crystals, in the part that looks like 
slag, while others find that contact along the sharpedgeof the crystal 
is the better arrangement. The adjustment of the silicon detector is 
found by pressing down the metal point on the silicon surface and 
moving the point around and varying the pressure until maximum 
effective results are obtained. The best arrangement of the Solari 
detector is that made with an iron and carbon rod with a drop of 
mercury between the rods. To obtain adjustment of this detector 
bring the ends of the rod together until the click of contact is heard 
in the telephone receiver; then separate the rods until a hissing sound 
is heard in the telephone. The drop of mercury used should be very 
small, about the size of a pin head, and the iron and carbon rods 
should just make contact with it. The filings for a coherer should be 
kept free of grease and should not be directly touched by the hand. 
To cleanse filings place them for about 12 minutes in a glass vessel 
containing a solution of liquid ammonia 2 parts and distilled water 
10 parts. After draining off the liquid, dry the filings thoroughly by 
heating on a stove. The tube containing the filings and the plugs 
may be cleansed by means of the same solution if necessary, similar 
care being taken in the drying. Experience has shown that as the 
signaling distance is increased the number of filings in the tube 
should be correspondingly increased, say, for distances over 4 miles 
about *4 i nc ^ between the plugs. The Slaby-Arco steel-silver filings 
coherer (page 90 ) has been found to be very efficient and reliable in 
the proportion of 88 parts steel to 12 parts pure silver filings. The 
steel filings should be coarse and about ^ inch long and nearly the 
same in thickness. 

A hard carbon similar to that used in arc lamps is suitable for 
microphone detectors. If trouble is experienced from the burning out 
of the Woolaston wire in amateur stations in the vicinity of high 
power installations it may be advisable to employ a thicker Woolaston 
wire or to reduce the number of wires in the aerial from, say, 4 wires 
to 2 or 1, when receiving, to reduce the received energy. It fre¬ 
quently happens that sounds are received in the telephone from 
nearby high power stations without the aid of a detector. For prac- 


ADJUSTING DETECTORS. 


291 



tical suggestions on learning the Morse alphabet, the care of ap¬ 
paratus, etc., see page 304. 

To facilitate the use of various mineral detectors holder a holder 
similar to that shown in Fig. 29 
is employed; the material such as 
carborundum, molybdenum, etc., are 
placed between the surfaces as indi¬ 
cated, with any degree of pressure. 

Other detector holders are arranged 
with a flat metal surface on the base 
of the holder with a vertical brass 
point above it; the mineral being 
placed between the flat surface and 
the point. 

Many amateur stations with short aerials are doubtless unable to 
get certain high power stations because of the greater wave length of 
the latter stations. Introducing a larger inductance in the tuning coil 
or aerial will frequently bring the stations into attunement. On the 
other hand, no doubt many stations having long horizontal wires over 
roofs are unable to get short wave signals. The remedy for the latter 
condition is to shorten the aerial, or perhaps a condenser in series in 
the aerial will be of utility here. 

On the approach of lightning storms it is best to disconnect all 
apparatus from the aerial and to connect the aerial to earth direct. A 
double pole double throw switch may be used for this purpose. See 
3 , Fig. 986, Chapter XII. See also Fig. 4 in this chapter. 

The approximate electrical energy required to transmit signals to a 
distance of 50 miles over water at night with efficient apparatus and 
with aerials, say, 60 feet high, is about 50 watts. As the energy re¬ 
quired may for practical purposes be considered to vary as the square 
of the distance, 4 times this energy or 200 watts would be required to 
cover 100 miles, and 12.5 watts to cover 25 miles. The receiving dis¬ 
tance with aerials of varying heights, using an electrolytic or equally 
sensitive detector, may be roughly placed at 150 to 200 miles with a 
30-foot antenna; 300 to 400 miles with a 50-foot aerial; 800 to 1,000 
with a 100-foot aerial; all over water. 

Many of the foregoing remarks are intended to be merely sug¬ 
gestive. One of the pleasures of experimenting with wireless teleg¬ 
raphy is the devising of new ways and means of producing the same 
or improved results. 







■leters n LC Meters n L C Meters n L C Meters n L C Meters n L C Meters n L C 


TABLE 


GIVING WAVE LENGTH IN METERS, FREQUENCY IN PERIODS PER SECOND, 
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APPENDIX. 

(Reference to page 38 .) 

THEORIES OF ELECTRIC-WAVE PROPAGATION - . 

Applying the electronic theory to electric-wave propagation, it 
is assumed that under the electric force established by a source of 
electromotive force, the opposite plates of the condenser or vertical 
wire are charged with positive and negative electrons, respectively, 
until the pressure breaks down the spark-gap, whereupon there is an 
oscillation of the electrons analogous to that assumed in the case of 
electric charges in a condenser. The electrons being, as it is assumed, 
center of force in the ether, when they thus oscillate produce strains 
and contractions in the ether, which it is also assumed are radiated 
in the manner described as detached lines of force. These forces 
reaching the receiving wire or wires produce an electric force under 
which the electrons are set into oscillations in those wires. 

A theory of electric-wave propagation, due to A. E. Kennedy, 
in the “ Electrical World and Engineer,” is as follows: 

“According to the measurements of Prof. J. J. Thomson, air 
at a pressure of 1-100 millimeter of mercury has a conductivity for' 
alternating currents approximately equal to that of a 25 per cent, 
aqueous solution of sulphuric acid. The latter is known to be 
roughly 1 mho-per-centimeter, so that a centimeter cube would have 
a resistance of about one ohm. Consequently, air at ordinary tem¬ 
peratures, and at a rarefaction 76,000 times greater than that at sea- 
level, has a conductivity some 20 times greater than that of ocean 
water, although about 600,000 times less than that of copper. If we 
apply the ordinary formula for finding the elevation corresponding to 
a given air rarefaction, we find that if the air had a uniform tem¬ 
perature of 0° C., the height of this stratum of air, with a rare¬ 
faction of 76,000, would be 55.77 miles. If the air had a uniform 
temperature of —50° C. this elevation would be reduced 18.3 per 
cent., or to 45.5 miles. The temperature of the earth’s atmosphere- 


204 


WIRELESS TELEGRAPHY. 


has only been measured within a range of a very few miles above 
the surface of the sea, and consequently the materials are not at 
hand for any precise calculation of the height of electrically con¬ 
ducting strata. It maybe safe to infer, however, that at an eleva¬ 
tion of about 50 miles a rarefaction exists which, at ordinary tem¬ 
peratures, accompanies a conductivity to low-frequency alternating 
currents about twenty times as great as that of ocean water. 

“There is well-known evidence that the waves of wireless teleg¬ 
raphy, propagated through the ether and atmosphere over the surface 
of the ocean, are reflected by that electrically conducting surface. On 
waves that are transmitted but a few miles the upper conducting 
strata of the atmosphere may have but little influence. On waves 
that are transmitted, however, to distances that are large by compari¬ 
son with 50 miles, it seems likely that the waves may also find an 
upper reflecting surface in the conducting rarefied strata of the air. 
It seems reasonable to infer that electromagnetic disturbances emitted 
from a wireless sending antennae spread horizontally outward, and 
also upward, until the conducting strata of the atmosphere are 
encountered, after which the waves will move horizontally outward 
in a 50-mile layer between the electrically reflecting surface of the 
ocean beneath and an electrically reflecting surface, or successive 
series of surfaces, in the rarefied air above. 

“If this reasoning is correct, the curvature of the earth plays no 
significant part in the phenomena, and beyond a radius of, say, 100 
miles from the transmitter, the waves are propagated with uniform 
attenuation cylindrically, as though in two-dimensional space. The 
problem of long-distance wireless wave transmission would then be 
reduced to the relatively simple condition of propagation in a plane, 
beyond a certain radius from the transmitting station. Outside this 
radius the voluminal energy of the waves would diminish in simple 
proportion to the distance, neglecting absorption losses at tho upper 
and lower reflecting surfaces, so that at twice the distance the energy 
per square meter of wave front would be halved. In the absence of 
such an upper reflecting surface the attenuation would be considera¬ 
bly greater. As soon as long-distance wireless waves come under the 
sway of accurate measurement, we may hope to find, from the observed 
attenuations, data for computing the electrical conditions of the 
upper atmosphere. If the attenuation is found to be nearly in sim- 


KENNEDY’S THEORY. 


295 


pie proportion to the distance, it would seem that the existence of 
the upper reflecting surface could be regarded as demonstrated.” 

Prof. J. A. Fleming, lecturing before the Royal Institute, London, 
expressed the following views in connection with the effect of the cur¬ 
vature of the earth upon the propagation of electric waves. The elec¬ 
tric waves employed in Marconi’s transatlantic tests were about 1000 
feet in length, which was not very small compared with the obstacles 
they had to encounter, that is, the hill of water formed by the curvature 
of the earth, which he calculated is about 110 miles above a straight 
line joining the Lizard and Newfoundland. The bending required, 
therefore, is not great compared with the distance, being comparable 
to a wave one one-hundredth of an inch in length bending round an 
obstacle one fifth of an inch high. He thought it an interesting ques¬ 
tion whether it is conceivably possible to send an electric wave around 
the world, and suggested that it is an interesting possibility. Water is 
opaque to the Hertzian waves, and he believed it likely that the upper 
strata of air, being highly rarefied, were also opaque to these waves. 
He imagined that by internal reflection between these two opacities 
a beam of rays could always, as it were, be confined between them, 
and so, provided the impulse was strong enough, it could be made to 
pass any distance sandwiched between them independently of the 
curvature of the earth. 

Another theory, advanced by Rankin Kennedy, is here extracted 
from the “ London Electrical Review,” Vol. L.: 

“The fact that Mr. Marconi has detected electromagnetic oscilla¬ 
tions at a distance of 1500 miles from their source on the globe puts 
a different complexion on the wave theory of propagation as applied 
to Marconi’s results. The result of the actual experiment cannot 
agree with the rectilinear propagation of the waves; the curvature of 
the globe seemingly having no effect, disposes of the straight-line 
propagation. A lamp, however powerful, placed at Land’s End could 
not throw a ray of light into a ship 1500 miles off; neither could an 
oscillator send waves around the earth if these waves travel in a 
straight line, as light does. To me it seems that the effects are not 
duo to ethereal waves traveling as light does, but to electrical oscilla¬ 
tions set up in the earth itself considered as a whole sphere, insulated 
in space, and the same effects can be reproduced on a small scale on 
a large ball, or artificial earth, as it might be called. 


WIRELESS TELEGRAPHY. 


296 

‘‘Imagine a large globe suspended in space, practically a good 
conductor. Electrically the globe is nominally neutral, no difference 

of electrieal potential existing between any 
portion; but let the electrical conditions be 
disturbed at any point—say that a sudden 
separation of electricity is made at the point 
A in Fig. la ; we know from common 
knowledge that the disturbance at a will be 
propagated all over the sphere, much in the 
same way as it would if the ball were of 
ivory and struck at a by another ball, 
every particle of the ball would be disturbed 
by the blow at a. Or consider the bale 
covered all over by a sea of water, and at 
.A a submarine mine to be exploded, throwing up the water. A wave, 
or rather a series of waves, would be set up which would travel 
around the whole ball. 

“In this view of the electromagnetic transmission of waves, we 
can imagine the rapid discharges at great potential at the point A 
agitating the whole electrical system of the earth, and that the earth 
is surrounded by an electrical atmosphere normally at rest and neutral, 
so that when disturbed at one point, this atmosphere vibrates or oscil¬ 
lates throughout its whole mass. And therefore there is no reason 
why communication between the antipodes, A and c, should not be 
practicable. A large globe upon which a spark coil and a radial con¬ 
ductor can be laid at A, as in a Marconi installation, could be utilized as 
a working model. There can be no doubt that a rapid and high poten¬ 
tial series of charges and discharges at A could be detected at B or c 
by a Branly tube or otherwise. 

“Considerations regarding results of experiments in laboratories 
or even within a few miles of area, are not of much value in this 
matter. Marconi has applied the test to the whole earth, with the 
result that, so far as one can foresee, every wireless telegram is actually 
an effect of the surface charge of the earth as a whole, and not at all 
due to radiant energy traveling in space like a ray of light. How¬ 
ever that may be, the subject now calls for very different treatment 
from that which it has hitherto received, not so much perhaps in the 
interest of wireless telegraphy as in the interest of fundamental knowl¬ 
edge. Whether the earth as a whole is electrified as a ball with a charge 





Taylor’s theory. 


297 


u-pon it matters little; if it is electrified, then the oscillator simply 
agitates this charge. Lord Kelvin forty years ago clearly proved the 
earth s surface to be charged, and suggested that the opposite charge 
might exist in the rarefied upper layer of the atmosphere; if this is 
so, then the gaseous dielectric is polarized vertically. He also pointed 
out that a very considerable electrification of the whole earth’s sur¬ 
face could be elfected by quite a small amount of charge. It is quite 
■conceivable, then, that the earth’s electrical equilibrium may be suf¬ 
ficiently disturbed by what seems a very feeble apparatus, compared 
with the dimensions of the globe, to operate the delicate detector on 
any part of its surface. 

This theory, of course, still rests upon the wave transmission, 
but not upon straight-line action, the vibrations being propagated 
through the mass, only it is not the matter which vibrates, but the 
electrical charge upon it. . . .” 

Dr. Lee De Forest, in the “Electrical World and Engineer,” 
May 17, 1902, writes: 

“. . . The grounded radiating wave will tend to follow and con¬ 
centrate upon that path affording greatest conductivity, . . . the earth 
will tend to absorb energy-waves whose electric lines of displacement 
are parallel thereto, and thus arises the necessity for vertical rather 
than horizontal antennae. . . . 

“As Hertz first pointed out, the energy of his wave decreases 
with the sine of the angle between the vector, leading from a point on 
its surface to the spark-gap, and the axis of the oscillator. Hence, 
the chief electrostatic energy also resides nearest the equatorial plane, 
at least over water where obstacles have not too far consumed the 
same. Very interesting in this connection are the experiments which 
have been made with receiving instruments attached to the upper 
ends of wires suspended from balloons at various distances from the 
sending antenna and at different altitudes. Thus Le Carme in his 
observations among the Alps obtained signals from a 54-yard wire 
suspended 654 yards directly above a similar upright on the earth’s 
surface, showing that the same did not give off a purely transverse 
wave. By Hertz’s theory this axial line was that of least radiation 
of energy. But when 3.7 miles from the sending wire, Le Carme 
reports signals obtainable at a greater height, 872 yards, thus illus¬ 
trating the upward expansion of the wave which accompanies its 
outward radiation. . . „ 


298 


WIRELESS TELEGRAPHY. 



Fig. 2a. 


“In this connection it is of interest to note that the best effects 
were obtained here when the receiving wire was twice the length of 
the sending upright. This was to be expected, inasmuch as the one 
was a freely oscillating, unearthed system; the other grounded and 
representing but one-quarter wave-length. From such observations is 
made clear the role which the earth plays in transmission in preventing 
the dispersion of the field into space—another instance of Nature’s 
mercifulness to man. . . . 

“Consider now the sending apparatus, using merely a capacity 
instead of ground connection. The reason that long-distance trans¬ 
mission is never accomplished by such arrangement is 
evident; but the influence of the earth as a conducting 
medium still exists, though diminished. If, as in Fig. 
2 a, we have two oppositely charged bodies, and near 
them a conducting plane M m, a portion of the lines of 
static displacement will run into the conductor as shown. 
When a discharge occurs between the two bodies all 
of the lines of force will not be sent off self-closed, but 
a portion will travel over or into the sheet m m. 
Thus if the capacity at base of the spark-gap lies in the vicinity 
of earth, and the system be set into sufficiently rapid oscillation 
relative to its dimensions, we will still have to a certain extent 
transmission over the conducting surface. A large portion of the 
lines, however, being self-closed, will radiate rectiliuearily into space, 
or be actually reflected from the earth’s surface. When the advancing 
wave-train encounters any conducting obstacle, sections of the lines 
of displacement composing such wave are cut out of it, as it were. 
The obstacle, if large relative to the wave-length, will cast an electro¬ 
magnetic shadow, but where the wave-length is of several hundred 
feet an ordinary upright conductor, owing to the phenomenon of 
diffraction, will not essentially shield another situated a little behind 
it. As Heaviside has so well illustrated, the lines of the displace¬ 
ment wave advancing in a direction normal to their length will cut 
into a metallic conductor in their path, and entering therein in direc¬ 
tions nearly perpendicular to the surface of the conductor, will, there¬ 
fore, travel up or down the same as tho wave advances. This action 
means merely the excitation in the skin of the conductor of actual 
conduction currents, of the same frequency as that of the exciting 
oscillation; or if this be strongly damped, or aperiodic, the single 



DE FOREST THEORIES. 


299 


impulsive charge will cause the conductor to discharge or oscillate at 
its own natural period of vibration. Thus the action upon the 
receiving upright is inductive, though not in the ordinary interpre¬ 
tation of the word. This, being a volume effect, would vary as the 
inverse cube of distance, while, were the action due simply to the 
static charge upon the top of the sending antenna, the law would be 
that of the inverse square; if from the wire, as the first power of the 
distance, as actually tested in the laboratory. Lietz, using as receivers 
a Klemencis thermo-element and Kuben’s bolometer, has found this 
law to be intermediary between the two. On the other hand, the 
inductive effects from the two forces increase as the square and the 
first power respectively of the intensity of the source. Ascoli, reasoning 
from Neuman’s formula, has shown that the mutual action between 
the two single antennae should vary directly as the product of their 
heights, or, if equal, as the square of one, and inversely as the dis¬ 
tance apart. Much data from the field corroborates the correctness 
of this law, making due allowance for the extra increase of range 
arising from better transmission over obstacles of the longer wave¬ 
lengths. With an antenna arrangement as shown in Fig. 3the 
quarter wave-length may be greatly increased, but there 
is also the liability of harmonics, or multiple vibrations, / 
from the antenna as a whole and its component parts. 

If its electromagnetic pulsations be too slow, they are un- 4 
accompanied by any alternating static field, and do not \ S 
emit radiant energy; the waves are not detached from 
the conductor, there is no Hertzian decrement of damping, Fig. 3 a. 
and any action at a distance is by simple induction.” 

In a further discussion of this general subject in the same period¬ 
ical, July 5, 1902, Dr. De Forest writes: 

“ . . . While true that Hertz’s most startling demonstration was 
that of the existence of free electromagnetic waves in the ether, as 
called for by Maxwell’s theory, identical save in frequency with 
polarized light waves, yet it was only by ‘ electrical oscillations ’ in 
conductors that these Hertzian waves were generated, and only again 
by the electrical oscillations induced in his resonators by the free ether 
waves that the existence of these latter was demonstrated. Hertz 
was first to show that these very high frequency oscillations traveled 
along conductors, that they existed in the skin of the metal only, 
that they were reflected, formed standing waves with nodes and loops, 




300 


WIRELESS TELEGRAPHY. 


that their energy was in turn electromagnetic and electrostatic, that 
in the limiting case of an infinitely thin wire of perfect conductivity 
the pure etheric wave of transverse electrical displacement, with a 
velocity of propagation equal to that of light, was obtained. By 
-common consent, then, such vibrations detached or traveling over a 
conducting surface have most appropriately been styled Hertzian 
waves. Most certainly also they are ‘ oscillating currents ’ when 
traversing conductors. This was Hertz’s demonstration. Oscillations 
from a Leyden-jar discharge, of frequency much less than those from 
Hertz’s radiator, are sometimes called Federsen oscillations. Obviously 
the border-line cannot be defined. But when an electrical system 
discharges, having so small a time constant that the pulsations occur 
at a rate of millions per second, we have very different conditions 
from those ordinarily classed with alternating or oscillatory currents. 
A large joortion of the energy is electrostatic, and the force there 
involved may be conceived as lines of electric displacement perpen¬ 
dicular to the conducting surface, traveling along it away from the 
source of energy, following any zigzag path, rounding corners, reflected 
wholly or in part at all such sudden changes in shape or nature of the 
conductor. If near the end of a wire conducting these electrical 
waves a second wire parallel to the first be placed, the wave-train will 
be in whole or in part transferred to the second wire, and will run 
along that unchanged in phase. If the second wire or a metallic 
sheet he near the first and 'perpendicular thereto, the electrostatic 
line of the wave cutting into this obstruction will 6xcite therein oscil¬ 
latory currents or waves of like frequency, which will in turn traverse 
the length and breadth of this second conductor. 

“Aside from simplest theoretical reasoning, the period of dis¬ 
charge of a vertical conductor to earth has been actually measured 
and found to be such as to make its height measure, approximately, 
one quarter of the wave-length of that oscillation. For a vertical 
wire of 54.5 yards, this means a frequency of 1,500,000 per second, 
assuming a velocity of propagation nearly that of light. In the 
laboratory with such frequencies we find all the wave phenomena and 
skin effect described above. Why not, then, in wireless telegraphy? 
We have a conducting plane surface, the sea, perpendicular to the 
oscillator at its base. Our lines of electrostatic displacement cannot 
penetrate this conductor, they must travel over it, be its contour 
what it will. By virtue of the tall oscillator, the crests or loops of 


Thompson’s model. 


301 


these displacement lines have been first well elevated (if the expres¬ 
sion may be allowed). A hundred or a thousand miles distant is a 
second elevated conductor, say at an angle of 90° to the first, perhaps 
at an angle of 45° with the sea surface. Nevertheless, it has a ver¬ 
tical component, such as must cut out a shadow in the advancing 
veitical lines of force. Oscillatory currents or Hertzian waves are 
excited in this conductor by the cutting into it of these static lines, 
posith e and negative \ and a sensitive detector inserted in this con¬ 
ductor, whether it lead to earth, 

capacity, or to a symmetrical 
oscillator system, will be affected 
by the passage of the wave. In 
speaking of oscillating currents 
carried by the conducting salt 
water, it may be well to remem¬ 
ber that with such frequencies 
as we have here, our ‘conduc¬ 
tor , has been well proven com¬ 
pletely opaque, and that only 
by such phenomena as the above 
can transmission occur.” 

Prof. S. P. Thompson has 
designed a model, shown in Fig. 

4a (reproduced from “ LTndus- 
trie Electrique,” July 10,1898), 
to illustrate in a tangible man¬ 
ner the oscillator, the propaga¬ 
tion and detection of electric 
waves, after the experiments of 

Dr. Hertz. The oscillator is Fig. Thompson’s Model. 
shown at A supported by frame¬ 
work. A row of leaden balls assumed to represent the ether are sus¬ 
pended as indicated, by pack-threads, which are attached to small hooks 
in the supporting beam. At the lower end the threads are fastened to 
the balls by small eyelets. The threads are connected together, two by 
two, in such away as to form a V-shaped suspension. This method of 
suspension virtually prevents longitudinal vibration, gives a certain 
uniformity to the movements of the balls, and, in a sense, makes 
them a continuous body or medium. The receiver is a ring, b, 





























302 


WIRELESS TELEGRAPHY. 


with knobs and an air-space to resemble the Hertz detector or reso¬ 
nator. This ring is upheld by three threads, one of which is fastened 
to a supporting thread of the nearest ball. The oscillator is arranged 
to vibrate at right angles to the supporting beam. When, therefore, 
it is caused to oscillate, it communicates transverse vibrations to the 
nearest ball. This in turn imparts energy to the next ball, and thus 
one ball after another is set in transverse vibration, while the direction 
of propagation of the wave is forward or longitudinal to the support¬ 
ing beam. When the ball nearest the detector is set in motion it 
imparts a circular oscillation to the latter, due to the trifilar suspen¬ 
sion of the ring, which motion is designed to illustrate the assumed 
circular electric oscillations in the Hertz ring form of detector. 

It is pointed out by M. Guillaume that this arrangement insures 
a more or less uniform oscillation of the balls, while it is assumed 
that the ether takes indifferently all possible modes of vibration; still, 
on the whole, the model is in his view very true, and a sufficiently 
accurate approximation to the ether-wave motion is obtained by 
making the period of vibration of tho balls superior to that of the 
exciter or oscillator. 

A resonance theory of electric-wave propagation, advanced by 
Dr. Koepsel, is based on the assumption that the capacity of the earth 
can be calculated from the formula for potential of a charged globe, 
which would give the earth a total capacity of but 708 microfarads. 
This formula, however, requires the oppositely charged surface to be 
at a distance which, relative to the radius of the sphere, is great, a 
condition which perhaps is not met in this instance. Assuming the 
capacity of the earth to be 708 microfarads, Dr. Koepsel calculates 
that given a vertical wire with a capacity of .009 microfarad, the 
ratio would be .000013. The potentials vary inversely as the capacity. 
Hence, assuming an E. M. F. of 100,000 volts on the vertical wire, 
the variation of potential would be 100,000 x .000013 = 1.3 volt. By 
increasing the number of vertical wires, say to 400, twenty inches 
apart, to give the system a capacity of about .11 microfarad, the 
respective ratios would be .00016 and the variations of the earth’s 
potential would be 16 volts. By still further lengthening the trans¬ 
mitted wave-length, Koepsel thinks that the vertical-wire system must 
act upon the earth, setting it into resonance as a tuning-fork placed on 
a resonance box sets the latter into resonant vibration, thereby largely 
amplifying the original effect. 


EHRET SYSTEM. 


303 


Another theory of electric-wave propagation, due to Lecher, is 
that the electric waves are transmitted along the earth’s crust as 
waves are along wires. Signals could in this way be transmitted 
around the earth if its potential could be raised a few volts. He 
assumes that the function of the vertical wire is to bring this about 
by conducting the opposite electrification away from the earth for 
some distance, say 150 feet, and then conducting it back again; hence 
its foot gets charged positively and negatively alternately, and these 
charges are transmitted at a rate depending on the dielectric constant 
and magnetic permeability of the earth. 

{Reference to page 22.) 

Lodge points out that “when the coatings of a Leyden jar are 
spread out it radiates better, owing to the fact that in true radiation 
the electrostatic and the magnetic energies are equal, whereas in a 
ring circuit the magnetic energy greatly predominates.” (“ Work of 
Hertz,” p. 5.) 


EHRET SELECTIVE WIRELESS SYSTEMS. 

A number of patents have been issued to Mr. C. D. Ehret for 
devices appertaining to wireless telegraphy, one of which may be 
briefly described. 

This system comprises a vertical wire in which is the primary 
coil of a transformer. In the secondary of the latter are an induct¬ 
ance, a capacity, and the primary of a second transformer. In the 
secondary of the second transformer are another inductance, capacity, 
and the primary of a third transformer. In the secondary of the 
latter are the usual detector and relay, and an additional inductance 
and capacity. 

These three circuits are, so to speak, arranged in tandem, and 
their adjustments are such that each has the same period, the 
product of the inductance and capacity of each circuit being equal. 
The circuits are so designed, however, that in the first circuit (the 
one next to the antenna) the capacity is large and the inductance is 
relatively small; in the second circuit the capacity is relatively smaller 
and the inductance is relatively greater; and so on to the third or 
coherer circuit. The object of this progressively increasing induct¬ 
ance and reciprocally diminishing capacity is to secure sharper selec¬ 
tivity, hence any stray harmonics will be obliterated. The chief 



304 


WIRELESS TELEGRAPHY. 


feature of this device is therefore progressively sharply selective- 
receiving circuits in order that only the desired electro-radiant energy 
may influence the receiving apparatus. 

Mr. Ehret has also devised several synchronous systems. In one 
of these systems a transmitter setting up a certain rate of oscil¬ 
lations is connected to one segment of a segmental disk. Another 
transmitter attuned to a different rate of oscillations is connected to 
another segment of the disk, and so on. A rotating arm or trailer 
attached to the antenna passes over the segments in rapid succes¬ 
sion; consequently waves of different periods are successively radiated 
from the vertical wire. If, then, at another receiving station there is 
a corresponding disk, to the respective segments of which are con¬ 
nected wires leading to receiving apparatus attuned to the respective 
transmitters, and a trailer rotating synchronously with the first-men¬ 
tioned trailer, each circuit will receive its allotted message. 

The same transmitting arrangement may be utilized to transmit 
different messages by one vertical wire to a number of different sta¬ 
tions, each attuned to the desired wave period and equipped with 
synchronous apparatus. 


THE BULL SELECTIVE WIRELESS TELEGRAPH. 

It was to be expected that variations from the beaten path of 
transmitting and receiving wireless telegraph signals by means of 
long and short trains of waves constituting the Morse alphabet would 
shortly appear. One such system, invented by Mr. Anders Bull, will 
be briefly described. Synchronously rotating disks are employed at 
the transmitting and receiving stations. A relay, whose armature 
acts like the key in the primary of an induction coil, is connected 
in such a way that when certain five contacts on the frame of a 
transmitting disk are consecutively closed, the oscillation circuit is- 
closed five times. These five contacts are fixed on the disk at pre¬ 
arranged intervals. Similar contacts are provided on the frame of 
the receiving disk, but these are arranged in series in such a manner 
that when all are closed, and not until then, a Morse register is 
actuated, marking a dot on a paper strip. 

In sending signals a Morse key is operated in the usual way. This 
key controls the relay, the armature of which normally holds a 
rotating wheel at rest bv means of a hook engaging Avitli a pin on the 



BULL SELECTIVE SYSTEM. 


305 


wheel. When the wheel is allowed to revolve this pin closes a circuit 
in which is a battery and an electromagnet. This latter magnet is; 
mounted in proximity to certain springs carried by the rotating disk. 
These springs are vertical and at their upper ends flexible. Normally 
they slide in a given channel or groove, in which they do not affect 
the five contacts before mentioned. When, however, the electromag¬ 
net on the disk is magnetized, it attracts one of the springs and 
switches it into another groove, where it impinges on the contact 
points and closes them. The receiving disk is similarly provided 
with vertical springs, which are diverted from the normal channel 
by a magnet controlled by the coherer. 

When the Morse key is depressed, therefore, as in making a dot, 
the small wheel is released and makes one revolution, when it is again 
held by the hook on the armature. During this revolution the mag¬ 
net at the transmitting disk has been closed, diverting one of the 
rotating springs into the channel, where they close the contacts and 
thereby transmit five impulses to the vertical wire. Concurrently, the 
coherer at the transmitting end is operated five times, closing the five 
contacts as stated, and recording a dot on the paper strip. When a 
dash is sent, the small wheel at the sending station makes two or 
three revolutions, and as a result two or three dots are recorded at the 
receiving end, these dots constituting a dash. 

As the disks at each station are assumed to rotate synchronously, 
it is evident that unless the contacts on the respective disks are placed 
at corresponding intervals on the disks correct signals will not be 
recorded by incoming waves. By this means a number of different 
prearranged dispositions of the contacts may he made around the 
disks, and in this way different stations may be selected as desired* 


{Reference to page 141.) 

By forming the bridges of the responder in a mechanical manner,, 
namely, by using fine platinum wires, .0001 inch diameter, with their 
ends very close together, in slightly acidulated water, De Forest finds 
that this anti-coherer is made absolutely reliable and much more sensi¬ 
tive than when the bridges are formed by the current. When the ends 
are withdrawn a counter E. M. F. of polarization is set up in the celk 
which makes the apparent conductivity of the cell practically nil. In¬ 
coming oscillations cause a temporary annulment of the insulating film' 
of oxygen gas surrounding the fine positive electrode, causing an 



306 


WIRELESS TELEGRAPHY. 


increase in the conductivity of the cell. The latter is a potential 
operated device. The variation of distance between the electrodes, 
therefore, changes the responder from a current-decreasing to a cur¬ 
rent-increasing device. The former will operate a relay. In either 
case two cells of battery are used in shunt with the detector. These 
detectors were employed in the recent successful experiments made 
with the De Forest system between Holyhead and Howth, Great 
Britain, a distance of sixty-five miles. 

(Reference to page 74.) 

PRACTICAL SUGGESTIONS FOR LEARNING CODES AND ON WIRELESS 

TELEGRAPH SIGNALING. 

The American Morse telegraph code, which is in use exclusively on 
land lines in the United States and Canada, is composed, as will be 
* seen by reference to page 74, of elements, termed dots, dashes, 
and spaces. These elements are formed by the length of time during 
which the key, or other transmitting instrument, may be held closed 
or open, the time of making a dot being taken as 1. The words 
“dot/’ “dash,” and “space,” therefore, stand for periods of time, so 
far as the transmission of signals is concerned; the received signals, 
however, when recorded on a paper strip, or sheet, are of course indi¬ 
cated as dots and dashes. Some of the letters of the American alpha¬ 
bet are composed of dots, some of dashes, others of dots and dashes, 
and others, again, of dots with spaces between. The latter are termed 
“ spaced ” letters. 

• ___ 

The telegraph code in use in Europe and other countries outside 

of the United States and Canada is known variously as the European, 
Continental, or Universal. This latter alphabet is also very generally 
used by all the wireless telegraph companies excepting the American. 
Doubtless it will eventually be employed as the international tele¬ 
graph signaling code. In the Continental or Universal alphabet, as 
may be observed on page 74, there are no “spaced” letters, that 
alphabet being made up of dots and dashes exclusively. 

In length or duration one dash is theoretically equal to three dots. 
The dots and dashes are separated bv intervals of time, termed spaces. 
The space between the elements ol a letter is equal to one dot, the 
space between letters of a word to three dots, the space between words 
to five dots. The interval in “spaced” letters of the American Morse 
code is equal to three dots. 



SUGGESTIONS ON WIRELESS SIGNALING. 307 

Before attempting to make, by means of the key, the letters forming 
the Morse alphabet, it is advisable that the beginner should familiarize 
himself with the characters of the code which he purposes to learn. 
This is best done, perhaps, by separating from the rest of the alpha¬ 
bet, first, all of the “ dot” letters, thus: E ., I . . , S . . . , Ii . . .. , 

P.; afterward, the letters and figures containing dashes only, 

thus: T —, M-, 0-(in the Universal Code), and so on. 

After the alphabet, figures, and the important punctuations have 
been fairly mastered, the student may then begin the practice of 
making the letters by means of the key. The student should bear in 
mind that he is dealing with time intervals, and not with dots and 
dashes as such, although it will perhaps assist him in his practice to 
imagine that as he is forming the characters they are being reproduced 
on the paper strip at the receiving end as dots and dashes. The 
length of those dots and dashes, and the length of the spaces between 
them, will therefore correspond with the time during which he holds 
his key closed or open. 

In making, for instance, the letter A, the key is pressed down 
firmly on its contact for a short time, then raised for an equal inter¬ 
val, then depressed for a time thrice as long as when making the dot, 
then raised. The letter B is formed by pressing the key down for a 
time equal to a dash, which act is quickly followed at regular intervals 
by three short depressions, or dots, and, of course, with spaces between. 

With the comparatively large keys that are used by a number of 
the wireless telegraph companies, the manner of holding the key is 
not so important. It is generally true of this system, as of ordinary 
Morse manual signaling, that each individual will ultimately adopt a 
style of manipulating the key that becomes as characteristic as one’s 
handwriting. An important point is to insure that all dots shall have 
the same duration; likewise that all spaces between elements of a let¬ 
ter shall be of uniform length; also that all dashes and spaces between 
letters shall be of equal length, and that all spaces between words 
shall be equal. For example, if at a certain rate of signaling the 
duration of a dot be .3 second, then the duration of a space between 
dots and dashes of a letter shall be .3 second; the duration of a dash 
shall be .9 second, the space between letters of a word shall be .9 
second, and the space between words shall be 1.5 second; all as near 
as may be. With a faster rate of signaling the duration of each ele¬ 
ment will be shorter, and with a slower rate of signaling each element 



o08 


WIRELESS TELEGRAPHY. 


will be longer. In holding down the key, sufficient time must be* 
allowed to permit the proper operation of the transmitting as well as 
the receiving apparatus; and where the type of receiving apparatus 
may not be known, as in the case of vessels at sea, it is advisable to 
err on the side of slowness. Between established stations the proper- 
speed attainable will quickly be ascertained. 

These codes may be and are also used in signaling with flash lan¬ 
tern, heliograph, search-light shutter, fog-horn, or steam-whistle. 
In fog-horn or steam-whistle signaling, one short “toot” represents 
a dot, a longer “ toot,” or blast, a dash; the duration of the toot and 
blast being relatively as in the case of the dot and dash. 

In the operation of Morse telegraphy it is the usual custom to 
allot each station a “call,” consisting of one or two letters of the 
alphabet. For example, “N,” “X,” “NY,” etc. To call up a 
station the letters allotted to that station are signaled repeatedly, 
followed by the “call” of the calling station. When, then, any sta¬ 
tion on a telegraph line hears his call being made (by sound), or sees 
it being recorded on the paper strip of a recording register, he opens 
his key and responds by saying, “ I I” (.. . .), and signing his “call,” 
whatever it may be. This is likewise the course pursued in heliograph, 
flag, or flash-light signaling. (It is the custom, also, for operators to 
have a certain letter or letters which they give when sending a mes¬ 
sage and when acknowledging the receipt of one. This, however, is* 
only really necessary when there is more than one operator in a sta¬ 
tion.) This process is also followed in wireless telegraphy when the 
calls of the station are known, except that in the ordinary arrange¬ 
ment of wireless apparatus at present the called operator cannot 
“break” in on the calling or sending operator, but must wait until 
the calling station ceases signaling before answering. In probably the 
majority of cases at the present time a call-bell operated by a relay is 
employed. Therefore, to call a station, the calling station by closing 
the transmitting key sets up a series of oscillations which operates the 
call-bell of any ship or other station within range. The answer may 
be made in the same manner, but to answer such a call it is better to 
signal “ I” three or more times, followed by the call of the acknowl¬ 
edging station. 

W T hen the call of any vessel or station is unknown, as will often 
happen in wireless communications between vessels at sea, lightships, 
and elsewhere, signal the letter A continuously and await at interval 


aj 


SUGGESTIONS ON WIRELESS SIGNALING. 


309 


an acknowledgment. This form of call will also attract the attention 
of stations that may employ the telephone receiver exclusively. To- 
interrupt a station, or -to stop the signals, the same character, A, may 
be signaled. 

When a station answers a call, the calling station may proceed to 
send the message practically as outlined in the following example: 

7 paid From SS March/ at sea June 24 1903 

To Captain Paul Jones 

A. (Or name of receiving station, if known.) 

Report shaft broken and repaired; all well 

Sg Captain A Braun. 

(Followed by call of sending station or call of operator; former pref¬ 
erable.) 

The letters “ Sg ” mean signature. The words ‘ ‘ 7 paid ” are termed 
the “ check,” and may be sent at the beginning or end of message. 
If message is “collect,” so mark it. 

Punctuation marks are used sparingly in telegraphy. Only the 
period and semicolon are used in this message, which, assuming the 
Continental alphabet to be used, would appear on the paper strip a& 
follows: 

a 


a 


If any part of a message is lost, the receiving station will make 
the fact known by requesting the sender to repeat the missing por¬ 
tion. The usual formula is to signal “G A” (go ahead), followed 
by the last word correctly received. To correct an error in sending,. 












310 


WIRELESS TELEGRAPHY. 


signal seven or more consecutive dots and resume the message, 
beginning with the last word correctly sent. When the message is 
received accurately, the reply 0 K, or other similar sign, is sent, 
with the signature or call of the receiving operator or station. It is 
advisable to slow down the speed of transmitting when an unusual 
word occurs in a message, and to insure accuracy it may be well to state 
after the end of the message, “that is,-,” repeating the word. 

Some of the foregoing methods for the transmission, reception, 
and correction of messages, and for calling and answering stations, 
are those adopted by the United States Signal Corps in all forms of 
flag, flash, and heliograph signaling, and are readily applicable to 
electric wireless signaling. (For further description of these forms 
of signaling, see author’s “American Telegraphy and Encyclopedia 
of the Telegraph.”) 

The preceding suggestions relate more particularly to reception by 
a recording instrument. When a telephone is employed as a receiver 
the receiving operator must be able to read by sound. The sounds 
received in the telephone consist of short and long tones (more or less 
broken, perhaps), which are read as dots and dashes respectively. To 
learn to read by sound, while a somewhat slow process, is not an arduous 
one, and when one is thoroughly familiar with the alphabet in which 
the signals are transmitted, a message slowly sent may be received 
after comparatively little practice, which remark also applies to fog¬ 
horn and whistle signaling. (See p. 197.) 

In transmitting signals, the switch is first turned to connect the 
transmitting circuit with the vertical wire. When the message is 
transmitted the switch is set for receiving and the acknowledgment 
of the distant station is awaited. The novice at transmitting will 
find it of advantage to have the characters of the alphabet printed on 
a sheet before him for immediate reference. Where registers or ink- 
ing-recorders are employed, it is advisable to set them in operation in 
advance, unless they are automatic in their action. Where call-bells 
are used, these should always be left in circuit awaiting communi¬ 
cations. For best results with the register the pull of the armature¬ 
spring should be gentle, or a slow-acting magnet should be used, in 
order that the armature-lever may stay down during the receipt of 
signals, its tendency being to rise or clatter with too strong a spring. 
(See remarks-on register, p. 196 ; also see “Adjustment of Apparatus,” 
Index, under “Apparatus.”) 



CARE OF APPARATUS. 


311 


The operator or attendant in charge of the apparatus should con¬ 
stantly be on the alert for imperfect or dirty contact-points, loose 
connections at binding-posts, run-down batteries, etc. The battery 
for the induction coil used in the majority of comparatively small 
installations requires very careful attention. For a ten-inch spark- 
coil, from 6 to 8 volts and 5 to 6 amperes may be necessary. Before 
the vibrator starts the current may run up to about 10 amperes; care 
is therefore essential to guard against the vibrator remaining idle when 
the battery circuit switches and key are closed, to avoid rapid running 
down of battery. The turns aiid resistance of the primary and sec¬ 
ondary wires are usually chosen to suit a given voltage and current. 
The contacts of the hammer interrupter are subject to quick disin¬ 
tegration, and require somewhat frequent attention and adjustment. 
When everything is in good order the vibrator of the induction coil 
begins vibrating as soon as all switches and the key are closed. Some¬ 
times a tap may be necessary to start it. By forestalling the defects 
indicated, and others of a more or less similar nature, many delays 
in operation will be avoided. 


(Reference to page 21.) 

Energy is also expended in radiating electric waves. Hertz, as a 
result of his dumb-bell oscillator experiments referred to (page 31), 
calculated that an initial stock of energy equal to 54,000 ergs in the 
oscillator would be radiated in about 11.25 complete oscillations, or 
at the rate of 2400 ergs per half-oscillation, the wave-length being 
about 100 centimeters and the length of the oscillator 100 centime¬ 
ters. To furnish energy amounting to 2400 ergs in 1.53 hundred- 
millionths of a second is equivalent to working at the rate of 22 horse¬ 
power. See “ Electric Waves/’ Hertz (Jones, translator), pp. 150. 

(.Reference to page 211.) 

For ordinary service the earthed antenna has been found satisfac¬ 
tory, but for tuned systems the direct earth connection is found to 
possess some disadvantages. Thus variations in the earth connection 
may disturb the tuning. For this and other technical reasons, such 
as the elimination of atmospheric interferences, a non-earthed aerial 
is sometimes employed. Lodge-Muirhead have used a wire netting 
or counterpoise with satisfactory results in an installation at Ileysham 
Harbor, England. (See page 82.) Wildman in Alaska, because of 





312 


WIRELESS TELEGRAPHY. 


the inability to get a good “earth 99 owing to the fact that the station 
is built on a glacier, has also successfully employed a non-earthed 
wire netting or counterpoise at some of the United States signal- 
corps stations. This counterpoise may be regarded as an inductive 
earth. 

(.Reference to pages 153 , 192.) 

ELECTROLYTIC DETECTORS. 

Fessenden has also devised a wave-detector of a type termed by 
him a liquid barretter and by others an electrolytic detector, which 
has been extensively employed in various forms. 

The Fessenden liquid barretter consists of a very fine platinum 
wire w (Fig. ba) dipping into an acid solution in a vessel v. The 
depth of immersion of the fine wire is regulated by the screw s, up¬ 
held by the support r. a is the 
connection to the vertical wire; w 
is the lower electrode, the size of 
which does not appear to be ma¬ 
terial; t is a telephone receiver; b 
is a small battery of dry cells; r is 
a resistance or potentiometer to reg¬ 
ulate the strength of current re¬ 
quired for polarization. The fine 
wire w is the positive electrode; 
w' is the negative electrode. A 
solution of 25 per cent, sulphuric 

Fig. 5a. Fessenden Detector. acid gives good results, but various 
acids and mixtures operate successfully. 

According to the electrolytic theory of operation of this detector, 
battery b develops a slight evolution of gas on the electrodes, setting 
up a counter-electromotive force of polarization, which has the effect 
of increasing the apparent resistance of the circuit. Electric oscilla¬ 
tions in the circuit cause a temporary reduction of the counter¬ 
electromotive force, whereby the current is increased and sounds are 
produced in the telephone receiver. Schloemilch has found that by 
choosing two electrodes in a polarization cell having as wide a differ¬ 
ence as possible in the series of electric potentials the battery b may 
be dispensed with. A crude but practical form of this detector is 
made by breaking off the upper part of an incandescent-lamp bulb, 























ELECTROLYTIC DETECTOR. 


313 


removing the filament and exposing the platinum terminals. A solu¬ 
tion of sulphuric acid is placed in the bulb, covering the platinum 
terminals. Another practical form is made by boring a bole in the 
end of a platinum wire about one-eighth inch in diameter. One or 
two drops of sulphuric-acid solution is placed in the cup thus formed. 
The fine platinum wire is then suitably placed in the solution. 

The diameter of the fine wire as used by Fessenden is given as 
about four one-hundred-thousandths of an inch. That used by 
De Forest and Schloemilch is given as about thirty-eight one-millionths 
of an inch. This extreme fineness of wire may not be absolutely 
necessary, since experiments with platinum electrodes more than one 
thousandth of an inch immersed in a solution of nitric acid have 
given satisfactory results at a distance exceeding two hundred miles. 
To prevent the tendency of the fine wire to float or turn up in the 
liquid, as well as to regulate the amount of wire exposed in the liquid, 
it is sometimes covered with a glass shield. This turning up of the 
wire may be overcome by forcibly submerging the wire and then with¬ 
drawing it to a desired distance. Extra heavy current oscillations in 
the circuit due to the close proximity of a transmitting station fre¬ 
quently burns off the fine wire, necessitating renewal of the tips. 
The fine wire employed for this purpose is usually silver-coated, the 
silver being eaten off to the desired extent by immersion in nitric acid. 

(Reference to page 207.) 

ELECTRIC-WAVE METERS. 

To facilitate the measurement of electric-wave lengths for wireless 
telegraph purposes at least two wave-meters are now in practical 
operation, namely, theDonitz wave-meter, by the Telefunken Wireless 
Telegraph Company, and the Fleming wave-meter, by the Marconi 
wireless interests. 

These wave-meters, or ondameters, are based primarily on the 
fact that with an exciting circuit in proximity to a secondary circuit 
a maximum current will be induced in the secondary circuit when 
the two circuits are in resonance, which will be when they possess 
corresponding inductance and capacity. Knowing the capacity and 
inductance of the secondary circuit, the frequency and wave-length 
of the oscillation are deducible. The period of an oscillation varies 
with the inductance and capacity of the circuit, according to the 



314 


WIRELESS TELEGRAPHY. 


formula T = 2tt k l. (See p. 21.) Hence it is evident that the 
frequency n of the oscillations (number per second) will be equal to 1 

divided by t, that is,ft=-i The velocity of propagation of the oscilla¬ 
tions or waves being 186,000 miles per second, the wave-length then 

v 

equals velocity divided by the frequency = —, or wave-length equals 

7% 

TV|/KL = 27TY |/k l. In ordinary practice resonance is indi¬ 
cated by the loudness of received signals in the telephone receiver. 


THE DONITZ WAYE-METER. 


rw. 



Fig. 6a. Donitz Wave-meter. 


The Donitz wave-meter is shown in Fig. 6a. It consists of a 
coil of wire.c, about eight inches in diameter, that may be placed or 
held in the vicinity of the field of force of the oscillating circuit to 

be measured. This coil is in series 
with a condenser K and another 
coil of wire c'. The latter coil is 
placed in inductive relation to a 
smaller secondary wire w', in the 
circuit of which is a small heat- 
wire h contained in one of the 
ends of a U-shaped tube t, partly 
filled with a colored liquid as in¬ 
dicated. The condenser K con¬ 
sists of two sets of semicircular metal plates, oue set fixed, the other 
movable to or from the fixed plates; the whole being contained in 
a glass case and immersed in oil. The movable plates of the con¬ 
denser are operated by means of a knob x, to which is also attached 
a pointer p, which moves around a graduated scale s. 

The capacity of this oscillation circuit varies with the adjustment 
of the condenser-plates. The condenser is then adjusted until the 
circuit is in resonance with the external oscillation circuit, which will 
be indicated when the heat-wire by expanding the gas in the tube 
forces the liquid in the other arm to a maximum height. The 
pointer p at this time will be opposite a given point on the scale, 
which is divided in such a way as to indicate the wave-length corre¬ 
sponding to the inductance and capacity of the wave-meter, which 
will also correspond with the wave-length of the external oscillating 
circuit. Obviously the scale could be arranged to indicate the fre- 












ELECTRIC WAVE-METERS. 


315 


quency of the wave instead of its length. The extent of the indica¬ 
tions in the tube is adjustable by varying the position of coils c' w' 
relative to one another. The coil c' indicates the oscillation circuit 
to be measured; for instance, a loop in the aerial circuit. In ordi¬ 
nary practice it is placed concentrically within coil c. For more ac¬ 
curate measurements, to avoid reactance effects from coil c, the coils 
should be separated about one inch. If removed too far, while the 
point of resonance will remain the same, the adjustment for resonance 
will not be so accurate. In measuring the primary oscillation circuit, 
coil c may be placed one foot or more therefrom. 

The apparatus is equipped with three inductance coils c of differ¬ 
ent values, and readily interchangeable in the wave-meter circuit. 
The respective value of these three inductance coils is so chosen that, 
depending on which coil is employed, the inductance of the oscillation 
circuit may be altered in the proportion ^ : 1 : 4, this giving the 
wave-meter a measurement capacity of from L equals 140 to L 
equals 1120. This wave-meter is quite compact and may readily be 
placed on a table one foot square, the containing box being about 10 
inches in height. (See U. S. patent No. 763,164.) 

THE FLEMING WAVE-METER. 

This meter comprises an arrangement whereby the inductance 
and capacity of the meter are increased or decreased simultaneously 
and in the same proportion by the movement of a handle; the condi¬ 
tion of maximum current strength in the meter oscillation circuit, and 
consequently of resonance with the external oscillation circuit, being- 
indicated by the maximum brilliancy of the glow m a sensitive neon 
tube. 

The device is shown in Fig. 7 a, in which s s is an inductance 
consisting of a spiral of No. 14 copper wire, wound on an ebonito 
tube cl. The turns of the spiral are about one eighth of an inch 
apart and cover about three feet of tube d. Over the left end of 
ebonite tube cl is placed a brass tube I forming one plate of a con¬ 
denser. J is another brass tube forming the other plate of the con¬ 
denser, these concentric cylinders being insulated from each other 
by a thin ebonite tube t. Tubes J and i are about 30 inches in 
length. A metal rod a and a sliding contact k are attached to the 
outer metallic tube J. The sliding contact k makes electrical con¬ 
nection with the spiral wire or inductance s, along which it is mova- 


316 


WIRELESS TELEGRAPHY. 


a 


f 




•y 

f 


31 

Ji min'" 

z 


ft 


c 

T n —I— I T T 


_Z ' 


* 


yMimimwrtWMtiwnwm'.irmmimwmiiimimmimrwimh'i 


Fig. 7a. Fleming W aye-meter. 


ble by means of insulated handle H. The same movement of the 
handle also moves the tube J more or less over the tube I. Thus, 
when the handle is moved to the right fewer turns of the wire are in 
the circuit, and less of the tube J covers tube I, and, consequently, 
the inductance and capacity respectively are diminished, and vice 
versa. 

The left end of the spiral wire S is open; its right end is con¬ 
nected to a pin p' on a bent metal rod L L. The left end of tube I is 
connected by pin p to the rod L L, which is about one inch wide and 

one-eighth inch thick. Thus 
the inductance and capacity 
are connected in series. The 
neon tube v is connected across 
the terminals of capacity, or 
condenser, j, i. In practice 
the neon tube consists of two 
bulbs connected by a narrow 
glass tube, generally construct¬ 
ed of uranium glass, and filled 
with rarefied carbonic-acid gas 
_.T preferably by the rare gas neon. This tube is carried by and 
moves with the metal tube J. The lower end of tube v is in prox¬ 
imity to the graduated scale C on the straight portion of rod L L 
as indicated, which is about six feet in length. The tube serves as a 
pointer or index. 

In the use of the instrument a part of the aerial wire in operation 
is laid parallel to the copper rod L l, and the handle h is moved back 
and forth until the point is found where the glow in the neon tube 
is brightest, at which time the oscillation circuits will be in resonance. 
The capacity and the inductance of the instrument in that position 
having been previously determined by laboratory tests, and the wave- 
frequency and wave-length corresponding to those factors having been 
previously calculated therefrom and marked upon the scale, the fre¬ 
quency and wave-length of the aerial may be ascertained from the 
scale without further trouble on the part of the observer. (See U. S. 
patent No. 804,190.) 


i 

































PART 2 


CONTENTS 


Introductory. 

. Electromagnetic 

CHAPTER I. 

PAGE 

. 1 

Induction Systems; High Frequency Gene- 


rators of Duddell, Poulsen, Marconi, Fessenden, Marjorana, 
Von Lepel, etc. 

CHAPTER II. 

The Ruhmer, Poulsen, De Forest Wireless Telephone 


Systems. 

. 15 


CHAPTER III. 


The Telefunken, Fessenden, Collins, Marjorana Wire¬ 
less Telephone Systems. 


24 






WIRELESS TELEPHONY 


CHAPTER I. 

INTRODUCTORY. 

ELECTROMAGNETIC INDUCTION SYSTEMS, LIGHT RAY TELEPHONY, SUS¬ 
TAINED HIGH FREQUENCY GENERATORS, ETC. 

The art of wireless telephony is not of immediately recent origin, 
and various instances and methods of speech transmission without 
wires have already been mentioned and described in Part 1 herein. 
Thus, Sir Wm. H. Preece in England transmitted speech by a mag¬ 
netic induction and electric conduction method between the Skerries 
Lightship and the mainland of Anglesey, a distance of three miles 
across water, as long ago as 1892-1898. (See page 12, Part 1.) 
Another type of wireless telephony also previously described is that 
in which variations in the luminosity of a beam of light are caused to 
reproduce speech at a distance. This device (page 174, Part 1), 
which in some measure is analogous to the latest developments of 
wireless telephony, is due to Bell, the inventor of electric wire teleph¬ 
ony. The distance to which speech has been transmitted by this 
device is very limited—about three or four hundred feet. 

Advancing somewhat along this line Simon discovered that if the 
resistance of the circuit of an arc light be disturbed by the introduc¬ 
tion of a telephone transmitter therein, the arc itself will reproduce 
speech spoken into the transmitter, (page 177, Part I.) Following 
Simon’s discovery Bell and Hayes found that the electric arc can be 
used as a transmitter of speech. This is accomplished (page 174) by 
placing the arc light in the centre of a parabolic reflector. A tele¬ 
phone microphone transmitter in shunt across the terminals of the 
arc light when spoken into causes variations in the luminosity of the 
arc, which, although not visible to the eye, can be detected by a suit- 




2 


WIRELESS TELEPHONY. 


able receiver in the focus of a distant parabolic reflector. As previ¬ 
ously noted (page 177), a small piece of carbonized material was 
used for the receiver; but other materials sensitive to heat were sug¬ 
gested. This general method of signaling without wires was much 
improved by Mr. Ernest Ruhmer, who, using a beam from a power¬ 
ful search light, and employing as a detector a sensitive selenium cell 
in the centre of a parabolic reflector, was able to transmit speech, due 
to variations in the beam of light caused by a telephone transmitter 
in shunt with the arc, to a distance of 12 miles. (See page 176.) 

In the foregoing systems of wireless telephony it will be observed 
that speech is transmitted by modifying the ether waves that consti¬ 
tute light. Systems of this kind, however successful they might other¬ 
wise be in actual operation, will obviously be limited as to distance 
of signaling by the actual distance at which artificial light is visible 
from a given source under favorable atmospheric conditions (about 
30 miles). In times of fog and heavy weather this distance would be 
much reduced. It was early recognized by workers in this field that 
if it should prove feasible to modify the electromagnetic waves em¬ 
ployed in wireless telegraphy by means, for instance, of the micro¬ 
phone transmitter, a wireless telephone system might be developed 
that would be operative at distances perhaps approximating that of 
wireless telegraphy, and that would not be limited in its operation by 
smoke, fog, or other more or less similar atmospheric conditions. 

But a difficulty in thus utilizing high frequency electromagnetic 
waves has been that these waves as ordinarily obtained from the dis¬ 
charges of the condenser in the spark gap oscillation circuit are very 
intermittent, being at best very quickly damped owing to heat losses 
in the circuit and to expenditure of energy in radiating the waves. 
In other words, the waves radiated are not persistent and their 
amplitude is not uniform. (See page 48, Part 1.) Assume 
for example that an alternating current generator developing a 
current of 60 cycles, or 120 alternations, per second, is the 
source of power. In that case there will be ordinarily 120 
sparks per second if each alternation charges the oscillation cir¬ 
cuit to sparking potential (which, however, is not always the case. 
See Transformers, Chapter XIV.) These discharges may be considered 
to give rise to oscillations in that circuit and in the aerial, of a fre¬ 
quency of, say, one million per second (a wave length of 300 meters) y 
the exact number depending of course on the inductance and capacity 


INTERMITTENT OSCILLATIONS. 


3 


of the oscillation and aerial circuits. In the case in point if the 
oscillations were sustained between discharges there would obviously be 
1,000,000 -f- 120 = 8,334 oscillations per spark. Because, however, 
of the damping effects mentioned these oscillations die out quickly, 
giving only from 2 or 3 strong oscillations in highly damped circuits 
to 10, 20 or 30 oscillations in less heavily damped circuits. Hence, 
oscillations are only developed during a very small fraction of the 
time between discharges, thus leaving a comparatively long interval, 
approximating the one hundred and twentieth of a second between 
the said discharges, during which time no oscillations are developed 
and no waves are radiated. For the purposes of wireless telegraph 
systems, however, in which the spark method of producing the oscilla¬ 
tions is employed (frequently termed “spark” telegraphy), the inter¬ 
val is rather beneficial than otherwise, inasmuch as it insures the 
desideratum of a high resistance circuit in the spark gap for the ensu¬ 
ing alternations. It may be noted that the term “jig” (plural “jigs”) 
has been suggested by Erskine-Murray, and is now sometimes used 
in literature to signify for brevity a train of high frequency electric 
waves or oscillations of the order employed in wireless telegraphy 
and telephony. The term “freque,” or “freques,” would perhaps be 
more suggestive and possibly quite as euphonious. 

In wireless spark telegraphy these intermittent oscillations are ob¬ 
servable in the telephone receiver as a musical tone, or buzz, which 
is broken into dots and dashes of the Morse alphabet by the telegraph 
key. If it were attempted to superpose vibrations corresponding to 
voice waves upon such intermittent oscillations the tone or buzz men¬ 
tioned would obviously render the reception of speech difficult if not 
impossible. Further, inasmuch as many of the overtones or upper 
harmonics that give quality to articulate speech consist of vibrations 
of 5,000 to 8,000 per second, it is evident that many of these over¬ 
tones would be lost during the pause between the oscillation trains, 
which would still further conduce to imperfect articulation. Ken- 
nelly has theoretically demonstrated that speech might be transmitted 
telephonically with harmonies not exceeding 2,000 per second. Fes¬ 
senden has, however, found by experiment that while fairly good 
transmission may be obtained with 5,000 interruptions per second, 
still for satisfactory wireless transmission of speech a frequency of 
at least 20,000 per second must be employed, otherwise disagreeable 
noises will be heard in the telephone receiver. 


4 


WIRELESS TELEPHONY. 


SUSTAINED HIGH FREQUENCY GENERATORS. 

Machine Oscillation Generators. —From the foregoing it is ap¬ 
parent that for successful wireless telephony, sustained oscillations of 
a fairly high order of frequency and of uniform amplitude are essen¬ 
tial. Accordingly a number of inventors have directed their efforts 
towards the production of a machine generator that will deliver a sus¬ 
tained alternating current of very high frequency, but hitherto not 
with much practical success, the irregularity of the machine pro¬ 
ducing noises in the telephone receiver that make the reception of 
speech difficult. Professor R. Fessenden has recently devised a gen¬ 
erator having an output of 2 kilowatts at a frequency of 80,000 cycles 
per second, at 8,340 revolutions per minute. The same inventor has 
also designed a machine to have an output of 10 kilowatts at 200,000 
cycles per second. These machines consist in general of a stationary 
disc armature of the Mordey type with a revolving field magnet hav¬ 
ing numerous polar projections. (See Fessenden Paper on Wireless 
Telephony. Trans. Am. Inst. El. Eng’rs, June, 1908.) Other 
workers have designed high frequency machine generators, but as a 
rule such machines develop very low power, the output apparently 
decreasing with the frequency. Thus Ruhmer’s machine of the in¬ 
ductor type with a frequency of 300,000 develops but .001 watt. Dud- 
delks inductor type of machine with a frequency of 120,000 has an 
output of .2 watt. In the inductor type of high frequency machine 
the armature and field are usually stationary, while in front of these 
parts a mass of iron with projecting teeth is caused to rotate at a 
high rate of speed, thereby causing rapid fluctuations in the magnetic 
relations of the field and armature. In other high frequency ma¬ 
chines the armature and field are caused to rotate in opposite direc¬ 
tions, in this respect somewhat resembling the revolving glass discs of 
certain static machines. This arrangement gives a high frequency at 
a comparatively slow rotation of the moving parts. 

With the machine generator of oscillations devised by Fessenden it 
is reported that speech has been transmitted between Brant Rock, 
Mass., near Boston, and a station in Long Island, outside of New 
York City, a distance of about 200 miles. Some details of this system 
will be given subsequently herein. 

Duddell’s Singing Arc.— Another entirely different method of ob¬ 
taining sustained oscillations is that due to Mr. W. Duddell, of Lon- 


DUDDELL SINGING ARC. 


5 


don, Eng., who discovered that when an arc lamp a Fig. 1, consisting 
of 2 solid carbon rods and taking a direct current of 3.5 amperes and 
42 volts (potential difference) supplied by dynamo D is in shunt 
with a capacity c of about 1 microfarad and an inductance l of 5 
millihenrys, a musical tone is set up in the arc and oscillations of a 
frequency of about 10,000 per second are established in the shunt 
circuit. Ultimately Mr. Duddell obtained frequencies of 30,000 to 
40,000 per second. A choke coil, not shown in Fig. 1, is inserted in 
the wires leading to the dynamo D to hold back the high frequency 
oscillations therefrom. 

Mr. Duddell’s explanation of the singing arc phenomena is that 
at the moment when the shunt circuit is completed a current flows 

from the arc into the condenser 



■wvw 


<f 

HH 


Fig. i. Duddell Singing Arc. 


circuit which decreases the cur¬ 
rent flowing in the arc. This in¬ 
creases the difference of potential 
between the terminals of the arc, 
causing still more current to 
flow in the condenser circuit and 
raising its potential above the 
normal voltage of the arc. In consequence of this the condenser be¬ 
gins thereupon to discharge back into the arc, increasing the current 
therein and reducing the potential difference between its terminals. 
The condenser now discharges too much and the reverse process is set 
up, and sustained or continuous oscillations are in this way main¬ 
tained in the shunt circuit. 

When sustained oscillations are comparatively smooth, or uniform 
in amplitude, and their frequency is above that to which the tele¬ 
phone or the human ear will respond, these oscillations are obviously 
not heard in the telephone receiver. Hence, if sustained oscillations 
of high frequency (inaudible) whether generated by a machine or by 
the arc, are to be utilized in wireless telegraphy some method of 
breaking the continuity of the waves has to be adopted, virtually as in 
certain Morse telegraph systems a continuous current is broken by a 
buzzer and is heard in the telephone as a tone or buzz. (See De 
Forest and Poulsen telephone systems herein.) While therefore the 
telephone will not respond to such high frequency continuous oscilla¬ 
tions, if the amplitude or contour of the oscillations be modified to a 
degree that comes within the range of receptivity of the telephone 






6 


WIRELESS TELEPHONY. 


receiver, as, for example, by speaking into a microphone transmitter 
placed in the oscillation circuit or in the aerial, instances of which 
will be given subsequently, the telephone will respond and will repro¬ 
duce speech spoken at the transmitter; practically as speech is repro¬ 
duced by modifying the amplitude of the waves of a beam of light in 
the cases cited. 

As long, however, as the frequency of the sustained oscillations of 
the singing arc was limited to, say, 30,000 to 40,000 per second, it 
was not anticipated by some authorities that much practical use 
could be made of these oscillations in wireless telegraphy or teleph¬ 
ony, owing chiefly to the weak magnetic effects at comparatively 
low frequencies, and the consequent inability to radiate electric waves 
possessing much energy. For unless the collapse of the static lines 
of force occurs with sufficient abruptness but little magnetic effect is 
produced and the lines are not whipped off into space, but are re¬ 
turned to the conductor. (See page 33, Part 1.) As previously 
noted, however, experiment seemingly indicates that the necessary 
whiplash effect is obtained with frequencies of 25,000 per second, 
but a much higher frequency than this is now employed in practice. 

Poulsen Oscillating Arc.— Fortunately several different methods of 
increasing the frequency of the arc oscillation generator were soon 
discovered. Thus Valdemar Poulsen found that if the singing arc 
is placed in an atmosphere of hydrogen, or other gas of high heat con¬ 
ductivity, the.frequency of the oscillations is increased to a remark¬ 
able degree, namely in some cases to 500,000 and 1,000,000 cycles per 
second, and over. It was also found that by burning the arc in com¬ 
pressed air or in steam the frequency of the arc oscillator is much 
increased. The flame from an alcohol lamp placed under the arc 
also has this effect. The cause of this increase of frequency when 
the arc is burned in an atmosphere of gas is not yet definitely known. 

The electrodes of the oscillating arc consist of a solid rod of carbon 
(the negative) and a copper tube (the positive). Poulsen having 
further found that by mechanically cooling the positive electrode the 
efficiency of the arc as a generator of oscillations is much increased, 
supplied a water jacket to the electrode through which a current of 
cold water circulates. One arrangement of the Poulsen device is out¬ 
lined in Fig. 2. The positive electrode consists of a copper ring c. 
This ring is mounted on a brass tube w, through which the water for 
cooling flows, c' is the carbon electrode. The arc is set up in a 


POULSEN OSCILLATING ARC. 


IV 

i 


closed box, into which the electrodes are introduced through opposite 
sides. Hydrogen gas or illuminating gas is regularly fed into the 
box. Also the inner poles m, m of an electromagnet are directed on 
the arc, the magnetic field of which forces the arc upward, forming 
an arch a between the copper and carbon electrodes, as indicated in 
Fig. 2, which lengthening of the arc increases its resistance and con¬ 
duces to greater variations in the potential of the arc. The coils of 
the electromagnet are in series with the arc as shown at m, m in 
Fig. 3, which figure depicts theoretically one scheme of the Poulsen 






Fig. 2. Poulsen Oscillating Arc. Fig. 3. 

oscillating arc circuits. The current employed is about 10 amperes. 
In Fig. 3 two oscillation circuits of the same frequency are shown, 
namely c', V a and c, l a. By this arrangement double electromotive 
force is developed, sc is the source of the direct current, t is a 
tuning coil, a is the aerial. In some instances Poulsen rotates the 
carbon electrode slowly by means of a small motor to prevent the 
formation of a carbon deposit on one part of the carbon electrode 
which would disturb the regularity of the arc. In other cases the 
arc is rotated for the same purpose by means of a rotary magnetic 
field. 

Thomson Oscillating Arc.—As precedence is sometimes attributed 
to Elihu Thomson as the inventor of the oscillating arc the following 
description of his device, from his United States patent No. 500,630, 
1893, may be of interest. In Fig. 4, m, n indicate the source of a 
500 volt direct current supply. 1 is an inductance coil, “to practically 
maintain the constant current flowing in the feeding circuit.” G is 
a discharge gap. m is a powerful electromagnet not always necessary, 
but the purpose of which is to break any arc in the spark gap. h 
is an inductance which if desired may be included in circuit with 
condenser k around the spark gap. According to the patent specifica- 

























8 


WIRELESS TELEPHONY. 


tions, to operate the apparatus the balls at o are first caused to touch, 
or a switch around them might be arranged to complete the circuit. 
Then the gap is adjusted so as to obtain between the balls an ap¬ 
parently continuous discharge. The separation at G tends to stop 
current passing thereat and to divert it to the condenser k . While 
the condenser is charging the arc is extinguished at G, the induc¬ 
tance i having limited the current from increasing to an amount 
sufficient to keep up the discharge at the gap while still charging the 



Fig. 4. Thomson Oscillating Arc. Fig. 5. Hozier-Broyvn Oscillation 

Generator. 


condenser. But the charging of the condenser which takes place 
very rapidly is attended with so great an increase of potential from 
its two sides that a spark or discharge again leaps at g and the con¬ 
denser at once discharges. The rupture of the spark or arc at G fol¬ 
lows immediately, the condenser again charges, and so on. It is a 
moot question whether this device produced sustained or unsustained 
oscillations. 

Hozier-Brown Oscillation Generator.— This is another method of 
producing sustained electric oscillations. It differs from the methods 
previously described, as may be seen by reference to Fig. 5. In this 
figure B is a block of copper resting loosely on the edge of an alumi¬ 
num disc D, which is kept in slow rotation. The contact of b, d is 
shunted by a resistance R, capacity c and inductance L. With direct 
current at 200 volts and with suitable adjustment of inductance and 
capacity, oscillations of the order of one million per second are set 
up in the shunt circuit, l' is an inductance in the supply circuit 
e, e to choke off the high frequency currents from the direct current 
generator. 

Marconi Sustained Oscillation Generator.—Signor Marconi has 
also developed a novel method of obtaining sustained oscillations in 


























MARCONI OSCILLATION GENERATOR. 


9 


which he avails of the fact that a true arc is not readily formed be¬ 
tween points in rapid motion. The arrangement for this purpose, 
which is in use in some of the Marconi trans-Atlantic stations, is 
shown in Fig. 6, in which d, d are metal discs about 2 feet in diame¬ 
ter, termed by Marconi polar discs. Between these discs is placed a 
“middle” disc M which is given a very high rotary motion by an 
electric motor or steam turbine. The polar discs are also rotated at 
a high speed, their peripheries being placed very near the edges of 
the middle disc. The discs are supported on framework, and are 
insulated from the earth and from one another, as indicated in the 
figure. In series with the polar discs are placed the inductances 
o, l' and condensers c, c. Between these condensers and the middle 
disc is the oscillation circuit consisting of an inductance l and capa¬ 
city c\ The inductance l constitutes the usual coupling to the aerial 
wire A. Contact is made with the middle disc by means of a brush 
b. In order to obtain best results Marconi finds that a peripheral 
6peed of over 300 feet per second is desirable, g is a source of elec¬ 
tromotive force. Connected with the polar discs as shown, r indicates 
the usual choke coils in the generator circuit. The inventor describes 
the probable operation of this device practically as follows. (See 

Transactions Royal Institution, London, March 13, 1908.) Imagine 

that the generator g is gradually charging condensers c, c and in¬ 
creasing the potential at the discs, say d, positively; d' negatively. 

Finally the resistance breaks 
down and a discharge takes place 
across one of the gaps, say, be¬ 
tween d' and M. This charges 
the condenser c', which then 
commences to oscillate and the 
charge in swinging back jumps 
from m to d, which is charged to 
the opposite potential. The 
charge of condenser c' will again 
reverse, picking up energy at 
each reversal from condensers 
c', c. This process goes on in- 
the oscillation circuit being re- 



aA 


Fig. 6. 


Marconi Oscillation Gen¬ 
erator. 

definitely the losses occurring in 
plenished by energy taken from the generator g. When the apparatus 
is rotated at the requisite speed the discharge that passes between the 
























10 


WIRELESS TELEPHONY. 


polar discs and the middle disc is, Marconi notes, neither an oscilla¬ 
tory spark nor an ordinary arc. If the disc is not rotated, or is 
rotated but slowly, an ordinary arc is established across the gaps and 
no oscillations take place. By this device frequencies of 200,000 per 
second are obtainable. The self cooling of the discs by their rapid 
rotation appears to be one of the conditions necessary for the pro¬ 
duction of the phenomena. The rotating disc is in close proximity 
to the fixed discs, only sufficient space for clearance being al¬ 
lowed. 

It was found that the oscillations set up by this apparatus were 
too continuous and of too high a frequency to operate a receiver such 
as the magnetic detector (page 188, Part 1), unless an interrupter is 
placed in one of the circuits of the receiver. To overcome this feature 
of the apparatus knobs k were placed on the middle disc, from which 
discharges take place at regular intervals. In this case, as the in¬ 
ventor states, the oscillations are not continuous, but consist of a 
regular succession of trains of undamped or slightly damped waves, 
and hence, it is possible to cause the groups of oscillations radiated 
to reproduce a musical note in the receiver, whereby it is easier to 
distinguish between the signals emanating from a transmitting station 
and the noises due to atmospheric electricity. By means of these 
sustained or semi-sustained oscillations, there is, it is stated, a 
noticeable improvement in the wireless telegraph signals received at 
the Marconi Glace Bay station from Poldhu. 


The Von Lepel Oscillator.—This device in one form consists 
of two copper plates c c Fig. 7, separated except at their centres 
by a sheet of thin paper. There is a round opening about half an 
inch in diameter in the paper, and it is at this point the spark is gen¬ 
erated. The copper plates are 5 inches in diameter. In reality 
each plate constitutes one end of two circular boxes, b, b each about. 
2 inches deep, provided with ventilation holes as indicated. Air 
pressure is conveyed to the chambers by rubber tubes t. The dis¬ 
tance between the respective plates is regulated by the screw s. d 
is a source of direct current at 500 volts, supplying 2.5 to 3.5 amperes, 
with the usual choke coils Z, V . The spark is shunted by the usual 
capacity c and inductance l. a is the aerial. The amplitude of the 
oscillations is modified by varying the inductance of the aerial by 


SUSTAINED OSCILLATIONS. 


11 



Fig. 7. Von Lepel Oscillator. 


means of the microphone transmitter circuit m, b', V. The rapid 

damping of the sparks that 
sets up the oscillations is 
apparently due to quick 
changes of temperature 
which changes are aided by 
the high heat conducting 
qualities of the copper 
plates and the cooling ef¬ 
fects of the air introduced 
into the respective cham¬ 
bers. The measured frequency of the oscillations is about one million 
per second. Tests by Shoemaker have shown that the oscillations set 
up in the aerial by this device are seemingly affected very slightly 
even by large variations of the aerial inductance and capacity. 

This oscillator has a well-defined critical point at which the 
oscillations are developed, but when this point is found the arc 
remains practically constant for hours. In another form of this 
oscillator two concentric cone-shaped chambers in close proximity 
are utilized. (See Von Lepel Wireless Telegraph System.) 

Notes on Sustained Oscillations in Wireless Telegraphy and 
Telephony.—The discovery of the oscillating arc by Duddell obviously 
paved the way for the use of sustained oscillations in wireless teleph¬ 
ony (and telegraphy), and Poulsen, Marjorana, and the Telefunken 
Wireless Company in Europe, and De Forest in this country, have 
made considerable progress in telephoning to a distance by modifica¬ 
tions thereof. 

A great advantage obtained by sustained oscillations in wireless 
telegraphy and telephony is that the property of resonance may be 
more fully availed of than with more or less intermittent oscillations. 
In some respects, however, perhaps sustained oscillations and the 
better resonance gained thereby may be of more utility for wireless 
telegraph purposes than for wireless telephony, especially as regards 
increased distance of transmission. This appears obvious if it be 
considered that in both wireless telegraphy and in wireless telephony 
the receiving apparatus is practically the same. In wireless teleg¬ 
raphy, however, the full effect of the radiated waves from maximum 
to zero is available, whereas only a comparatively small portion of 
the emitted wave energy, namely the modifications of the wave 














12 


WIRELESS TELEPHONY. 


energy due to the action of the microphone transmitter (about five 
per cent, of the total energy it has been estimated), is available in 
wireless telephony. Improvements in the direction of more powerful 
telephone transmitters whereby a larger percentage of variation in 
the amplitude of the waves may be obtained are now to be looked 
for. Fessenden has already devised one or more special forms of 
transmitter for use in wireless telephony from which he anticipates 
a variation of at least 25 per cent. 

When the oscillating arc is employed in practice the inductance 
is usually made part of a transformer, the secondary coil of which, 
or the coil itself, is placed in the aerial wire circuits as outlined in 
6ome of the following figures. De Forest modifies the oscillations by 
placing a microphone transmitter directly in the aerial wire. Poulsen 
does this by means of a microphone transmitter, inductively con¬ 
nected with the supply or feed circuit of the arc. Fessenden modifies 
the oscillations set up by the machine generator, either by means of a 
microphone transmitter in the generator circuit (the generator and 
transmitter being connected in the aerial circuit), or by causing a 
transmitter to vary the capacity of a condenser in the oscillation 
circuit, and in other ways described subsequently. Ruhmer proposed 
to modify the oscillations by placing a microphone transmitter in the 
field circuit of the machine generator. Campos places the microphone 
across the inductance of the oscillation circuit. In the Telefunken 
system the microphone transmitter is usually placed in parallel with 
the secondary of the transformer in the aerial circuit. 

The capacity employed in the arc oscillation circuit is compara¬ 
tively small, in some installations, about .006 microfarad. The oscil¬ 
lating arc requires for its proper operation in producing oscillations 
in the shunt circuit, a current of a certain strength and a certain 
leDgth of arc. For instance, Poulsen has found that with a difference 
of potential of 220 volts at the arc it ceases to set up oscillations 
when the current falls below 6 amperes with a water-cooled positive 
electrode, and below 4 amperes with a non-cooled electrode. Ruhmer 
found this critical value, with an electromotive force of 220 volts 
and a frequency of 500,000, to be about 5 amperes. 

A sensitive auto-detector such as is employed in wireless telegraphy 
is used as a receiver in wireless telephony. Fessenden utilizes the 
electrolytic detector or liquid barretter, Poulsen and the Telefunken 
Company a thermo-electric couple or an electrolytic detector, while 


SUSTAINED OSCILLATIONS. 


13 


De Forest and Marjorana employ the audion and the perikon de¬ 
tectors, all in combination with a telephone receiver. The filings 
coherer obviously is not adapted to wireless telephony, owing to its 
sluggish action. Fessenden’s experiments have shown that a receiver 
which restores itself in .0001 second is sufficiently rapid in action 
for wireless telephony. 

The Telefunken Wireless Telegraph Company, in conducting wire¬ 
less telephone tests in this country and in Europe, employ the singing 
are burning in air with a water-cooled copper electrode. It having 
been found that with the arc burning in air the frequency of the 
oscillation is increased by putting a number of arcs in series, the 
Telef unken Company place 6 of the arcs in series on a 220-volt supply 
circuit, and 12 arcs in a 440-volt supply circuit, as described more 
fully subsequently. 

The experiments in wireless telephony in which the single arc 
oscillator is employed indicate that considerable difficulty has been 
met with in maintaining a uniform tone of the voice in the telephone; 
the words being received in alternately low and high tones, rendering 
speech indistinct. This is doubtless due to packing of the trans¬ 
mitter or to irregularity in the operation of the arc. 

Notwithstanding the fair measure of success that has attended the 
operation of wireless telephony thus far by means of arc-obtained 
oscillations, it is thought in some quarters that this method will 
eventually be superseded by improved forms of high frequency ma¬ 
chine generators, owing to the irregularity of operation of the arc 
and also because of the limited amount of energy developed thereby. 
The mechanical and economical problems in the way of producing 
a successful high frequency machine generator are recognized to be 
difficult, but are not thought to be incapable of ultimate successful 
solution. On the other hand, the comparative simplicity and econ¬ 
omy of the arc method and the small space required for the appa¬ 
ratus are marked advantages in its favor. It is not improbable that 
if simultaneous wireless telegraphy from many near-by stations is to 
be practiced successfully a sustained oscillations method of signaling 
may have to be more or less universally adopted ultimately, inas¬ 
much as the general employment of this method would admit of 
selective signaling by the use of different wave lengths of a small 
percentage of variation virtually without interference, as noted sub¬ 
sequently in connection wuth the Poulsen system. With the spark 


14 


WIRELESS TELEPHONY. 


method of wireless telegraph transmission, especially on close-coupled 
systems emitting explosive trains of highly damped waves, it is gen¬ 
erally admitted that the simultaneous operation of adjacent powerful 
stations is well nigh impracticable, as such discharges are found to 
produce interference even in well syntonized and screened receiving 
circuits. The sustained oscillation method of signaling has the 
further advantage that it eliminates the difficulties of sparking at 
the transmitting key, as well as the noise of the spark, and, owing 
to the low potential employed as compared with spark telegraphy 
(1,000 volts as against 10,000 to 40,000 volts at the transmitter ap¬ 
paratus and 3,000 volts as against 100,000 volts and over at the top 
of aerial), the necessity for extraordinary care in the insulation is 
not so great as in the spark method. Poulsen’s experiments appear 
to show also that with the sustained oscillation method the distance 
of signaling over mountainous country, with equal conditions as to 
wave length, energy output, etc., is largely increased over the spark 
method, while the disturbances due to atmospheric discharges are 
much less pronounced in the case of the sustained oscillation method 
than in that of the 6park telegraph method. 


CHAPTER II. 



I 

THE RUHMER, POULSEN, DE FOREST WIRELESS 

TELEPHONE SYSTEMS. 


THE RUIIMER WIRELESS TELEPHONE. 


Figs. 8 and 8a show diagramatically the transmitting and receiving 
circuits of a wireless telephone system as arranged by Ruhmer, in 
which the singing arc as a generator of oscillations is employed. In 
Fig. 8 m is a microphone transmitter, t is an induction coil, d is the 
source of direct current, a is the singing arc burning in an atmos¬ 
phere of hydrogen or other suitable gas. c i' comprise the capacity 
and inductance in shunt with the arc. The oscillations are thrown 
upon the aerial wire inductively by the oscillation transformer i\ 
N, n are choke coils in the direct current supply circuit for the usual 
purpose. 


|A 





Fig. 8. Ruhmer’s Wireless Telephone. Theory. Fig. 8a. 


In Fig. 8 a, a is the aerial wire which is tuned by means of the 
sliding contact s to the frequency of the incoming electric waves, 
in the usual way, d is an electrolytic detector; b is the battery there¬ 
for. t is a telephone receiver. 


15 
















16 


WIRELESS TELEPHONY. 


Ruhmer reports successful transmission of speech with this ar¬ 
rangement, in 1906, over a distance of about 1,500 feet, with aerials 
60 feet high. The electromotive force employed was 440 volts. 


POULSEN WIRELESS TELEPHONE SYSTEM. 

The transmitting and receiving circuits of this system are shown 
theoretically in Figs. 9, 10. In Fig. 9, g is the source of direct 
current, c, c are the condensers of the oscillation circuit so ar¬ 
ranged as to insulate the arc and also to shut off the direct current 
from the aerial. These condensers consist of zinc plates in oil, each 
plate .11 inch apart. For varying the wave length a variable con¬ 
denser (vc Fig. 11) is placed in parallel with condensers c, c. The 
inductance I of the aerial circuit also forms a part of the inductance 
of the oscillation circuit, a is the oscillating arc, the water-cooling 
devices and electromagnets shown in Fig. 2 being omitted from Fig. 
9. M is a microphone transmitter inductively connected with the 



Fig. g. Poulsen's Wireless Telephone. Theory. Fig. io. 


supply circuit for speech transmission. In this figure direct coupling 
of the oscillation circuit to the aerial is shown. In Fig. 10 the re¬ 
ceiving circuit is inductively coupled to the aerial by the oscillation 
transformer I. c is a variable condenser in the aerial for tuning. 
c, d, t, b are the customary condenser, detector, head telephones and 
battery of the receiving circuit. 

In the latest apparatus of the Poulsen arc system the gas atmos¬ 
phere in which the arc burns is supplied by alcohol which is allowed 
to enter the arc chamber drop by drop; one or two drops per second 
being ample for an output of 1 kilowatt. In order to obviate the 
difficulties due to heating, inherent in the use of the microphone 
transmitter, by the strong currents met with in wireless telephony, 
4 to 5 amperes or more, as well as to obtain greater variation of 
resistance of the aerial circuit, hence greater modifications of ampli- 



















ARC WIRELESS TELEGRAPH. 


ir 


tude of the oscillations, Poulsen in one arrangement employs a micro- 
phonic transmitter consisting of 8 separate carbon granular trans¬ 
mitters in the aerial circuit. This multiple transmitter has eight 
separate tubes leading from one mouthpiece to the respective dia¬ 
phragms. 

At the Poulsen station at Lyngby, Denmark, the aerial is upheld 
by two masts 200 feet in height and 275 feet apart. A wire net 
constituting a counterpoise is suspended a few feet above the ground. 
The output of the generator at this station is 10 kilowatts at 500 
volts. At the Poulsen station at Cullercoats, near New Castle, Eng., 
the aerial is of the umbrella type, the wires being supported by a 
wooden lattice tower 220 feet high and 2 feet square at the base. The 
umbrella is 220 feet in diameter and is made in two folds, each of 
which consists of 12 phosphor bronze wires arranged in a semicircle. 
The upper end of each fold is connected with a vertical cable by 
means of which the umbrella portion of the antenna is connected with 
the operating room. By this arrangement the aerial may be operated 
as a loop or as a single aerial. 

At the Cullercoats station provision is made for wireless spark 
telegraphy by the De Forest system, and for wireless telephony and 
telegraphy by the Poulsen arc. For spark telegraphy a 5-kilowatt 
generator developing 400 volts, 14 amperes at 120 cycles, is employed. 
This is raised to 50,000 volts at the secondary terminals of a dry 
transformer. Leyden jars and inductance coils are employed in the 
usual manner in the transmitter oscillation circuit. The audion 
and other detectors and telephones are employed as receivers. The 
Poulsen arc method of wireless telephony has already been described. 
The circuit connections for wireless telegraphy by the arc method 
are outlined in Figs. 11, 12. The method of transmission adopted 
by Poulsen for arc wireless telegraphy is to cause the Morse key k 
to short circuit a few turns of the auto transformer t, as indicated 
in Fig. 11. This by prior adjustment brings the transmitting circuit 
exactly into tune with the receiving circuit, with the result that the 
apparatus in the sharply tuned receiver circuit is affected. When the 
key is open the two circuits are out of tune and the receiving circuit 
does not respond, vc is a variable tuning condenser. 

The receiving arrangement for Poulsen arc telegraphy is outlined 
in Fig. 12. Thus a third condenser v is interposed at rapid intervals 
between the terminals of the telephone t by means of a “ticker,” 


18 


WIRELESS TELEPHONY. 


consisting of a pair of vibrating contacts operated by an electro¬ 
magnet m. The contacts of the vibrating arm consist of crossed 
gold wires x. During the time that the transmitter and receiver cir¬ 
cuits are in syntony (the key being closed), continuous oscillations 
are received in the receiver circuit, and, while the ticker circuit is 
closed, the third condenser v accumulates a part of the received 
energy, which is discharged through the telephone receiver when the 
ticker circuit is open, whereby sounds corresponding to the dots and 
dashes transmitted are heard in the telephone. To avoid the noise 
from the magnetic vibrator, it is placed in a sound-proof receptacle. 


0 


Fig. ii. Poulsen Arc Wireless Telegraph. Fig. 12. 

The wave lengths employed in this system of wireless telegraphy 
range from 1,200 to 1,500 meters, equal to a frequency of 250,000 to 
200,000 per second respectively. The current strength in the aerial 
is about 10 amperes. The other apparatus indicated in Figs. 11, 12, 
are similar to that described in connection with Figs. 9, 10. As in 
Fig. 10 and Fig. 12, the coupling is very loose, the sharpness of tun¬ 
ing is very pronounced, a variation of 1 per cent, in the wave length 
placing the system out of tune. Thus, if the wave length is 600 
meters, a variation of 6 meters will produce dissonance. As wave 
lengths varying from 300 to 3,000 meters may be employed in this 
system, it is clear that on the foregoing basis several hundred stations 
may communicate in different wave lengths without interference. 

According to a statement by Poulsen, he has recently effected 
successful wireless telephony to a distance of 170 miles between two 
stations in Denmark, with masts 200 feet high. The primary energy 
is 900 watts, the radiated energy 300 watts; wave length about 3,600 
feet. Wi'h an increased energy output a phonographic record was 
transmitted by this system from the Poulsen Weissensee station near 
Berlin to the Poulsen station at Lyngby, a distance of 325 miles. 



























DE FOREST WIRELESS TELEPHONE. 


19 


THE DE FOREST WIRELESS TELEPHONE. 

In this system the arc method of generating sustained oscillations 
is employed, as already stated. In Figs. 13, 14, the transmitting 
and receiving circuits are respectively outlined in theory. In Fig. 
13, c is a variable capacity; i is an inductance, being the primary 
of a transformer the secondary of which is in series with the aerial 
wire a, and a microphone transmitter M. De Forest places the micro¬ 
phone between the secondary of transformer i and the earth, the 
nodal point of potential being at the ground terminal of the aerial; 
consequently the arcing in the microphone chamber will be least in 
that position, a is the oscillating arc with copper-carbon electrodes, 
burning in the flame of an alcohol lamp l. s is the source of a 220 
or 440-volt direct current supply, k, k are choke coils in the supply 
circuit for the usual purpose of shutting out the high frequency 
oscillations from the dynamo machine. The principle of operation 
of this oscillation generator is practically similar to that of the 
other arc oscillation generators described herein. The arc sets up in 
the circuit a, c, i, sustained oscillations that are radiated as electric 
waves from the antenna. Speech 6poken into the microphone M 
modifies the amplitude of these waves to an extent corresponding to 



Fig. 13. De Forest Wireless Telephone. Theory. Fig. 14. 


the effect of the air vibrations upon the resistance of the microphone 
circuit, thereby reproducing speech at the distant telephone receiver. 
The indicated current strength in the aerial, and consequently in the 
microphone transmitter circuit, is about 1.5 amperes. 

The receiving circuit connections and apparatus of this system. 
Fig. 14, are very similar to those of the De Forest wireless telegraph, 
in which a detector termed the audion is employed. This detector 
is primarily based on the Elster-Geitel bulb, described elsewhere (see 





















WIRELESS TELEPHONY. 


20 

Chapter XIV), but in the andion De Forest has added certain 
features which appear to be essential to its success as a detector of 
electric waves. 

Since its advent in 1906 the audion has undergone a number of 
variations as to the arrangement of its parts. In Fig. 14 it comprises 
a tantalum filament f between a grid g formed of No. 22 platinum 
wire, and a platinum wing, or small plate, w , within a small exhausted 
bulb b, resembling a 6-volt low candle-power lamp. The wing w is 
about .1 inch from the filament, which is made incandescent by cur¬ 
rent from a 3-cell storage battery b ; the current strength being regu¬ 
lated by a variable resistance r. t is a telephone receiver, b is a 
“potential” battery of 10 to 30 volts, adjustable as to potential. One 
terminal of the oscillation circuit is connected to grid g; the other 
terminal to the filament, as in the figure. 

Battery b is found to be an essential to the operation of the audion; 
causing it, according to the inventor, to act as a relay to the Hertzian 
wave energy. When properly adjusted as to heating battery b and 
potential battery b, the audion is very sensitive and produces loud 
sounds in the telephone. 

As previously noted herein, the incoming high frequency sustained 
oscillations due to the arc sustained oscillations employed in this 
system do not perceptibly affect the detector, owing to their 
uniformity and high frequency, but the modifications of those 
waves due to the action of the microphone transmitters, being 
within the range of the detector and the human ear, are heard 
in the telephone as articulate speech. The incoming oscillations 
appear to vary the resistance of the ionized gas in the audion 
in consonance with the variation of the resistance caused by 
the voice at the microphone transmitter, thereby reproducing speech. 
When the audion is employed in spark wireless telegraphy it responds 
to the long and short trains of damped waves in a manner analogous 
to the other auto-detectors described in previous chapters herein. 

In Fig. 15 is outlined the latest arrangement of transmitter cir¬ 
cuits of the He Forest wireless telephone system, dc is a direct cur¬ 
rent dynamo supplying 220 or 440 volts, depending on the distance to 
be signaled over. Only one oscillating arc a is employed. When 
440 volts are used the gap between the carbon electrode o and copper 
electrode c' is increased. The copper electrode is a hollow cylinder 
through which by suitable devices water is circulated for cooling 


DE FOREST TRANSMITTING CIRCUITS. 


21 


purposes, r is a reservoir for alcohol used for the lamp L. vc is a 
variable condenser in parallel with condenser b and, when additional 
capacity is required, also in parallel with condenser b', by means of 
switches n, n'. One of the serious troubles in the original oscillating 
arc in this system was due to the frequent stopping of the arc. To 
overcome this defect a solenoid w is now utilized in shunt with the 
carbon electrode to re-strike the arc automatically. By this device 
the oscillations are maintained steadily for an hour or more at a 
time. The amount of current supplied to the solenoid is regulated by 
a rheostat r. m is a small incandescent lamp in the power circuit 
which lights up when the apparatus is set for transmitting, t is a 



Fig. 15. De Forest Wireless Telephone. Transmitter Circuits. 


compact flat spiral oscillation transformer in which the primary p 
and secondary s are placed side by side. 1 is a small incandescent 
lamp lighted inductively by spiral p, this indicating when the oscil¬ 
lation circuit is in operation, h is a wedge which, when inserted 
between strips q, q' of the listening in key switch x, sets the circuits 
for transmitting, as in the figure. When h is withdrawn the aerial 
is connected in a loop t, t with the tuning coil of the receiver, m 
is the microphone transmitter, consisting of two carbon granular 
transmitters in series, responsive to one mouthpiece. A buzzer or 
“chopper” i is used for calling and to break up the sustained oscil¬ 
lations in the aerial into a tone for wireless telegraph signaling. 
Morse key k controls the chopper by opening and closing the circuit 
of battery b, and whereby the usual telegraph alphabet may be em¬ 
ployed. s' is a switch by which the microphone transmitter or the 
chopper may be inserted alternately in the aerial circuit as desired. 
H is a hot wire ammeter. 

Fig. 16 is a photograph of the De Forest wireless telephone ap- 





























22 


WIRELESS TELEPHONY. 


paratus as arranged in practice. M is the double microphone trans¬ 
mitter. i is a pilot lamp; m in Fig. 15. h is the key switch by 
means of which the circuit is set for transmitting or receiving. I is 
a handle by which the turns on secondary of transformer t, Fig. 15, 
are varied, n is the alcohol tank, a is a tube by which alcohol is 
fed to the lamp in the arc chamber, w indicates the solenoid; w ' 
the chimney for alcohol lamp, i is the chopper, k the Morse tele¬ 
graph key. l is a “pancake” form of receiver transformer or tuner. 
f, f are two audion detectors, either of which, or a perikon detector 
p, may be switched into the receiver circuit at will, v is a variable 
condenser in the audion circuit. The potential battery is contained 
in a case; the number of cells in use being variable in steps of 2 and 
3 by the lower and upper dial switches, b,b, respectively. 

In the latest form of this apparatus some changes have been made 
in the disposition of the alcohol chamber; also the pancake tuner 
has been displaced by an oscillation transformer in which the primary 



Fig. i6. De Forest Wireless Telephone Apparatus. 

coil is movable in and out of the secondary coil as required for 
adjustment. 

The De Forest wireless telephonic system is exploited by the Radio 
Telephone Company. One of the important stations of this company 
is located in the heart of New York City. At this station the antenna 
is supported by a steel tower 125 feet high on the roof of a 12-story 
building. The highest point of the tower is 310 feet above the 
street. The antenna consists of 8 stranded wires that drop down to 
the edge of the roof of the building. Each wire is made up of 7 








DE FOREST WIRELESS TESTS. 


23 


No. 20 B and S phosphor-bronze wires. The wires are suspended by 
a cross arm from the top of the tower and by means of a pulley and 
halyards may be made to face in any direction, as desired. The 
De Forest system was installed experimentally in the wireless tele¬ 
graph station on the Eiffel Tower, Paris, 1,000 feet in height, from 
which station phonographic records are reported to have been heard 
at a distance of 400 miles. 

The De Forest wireless telephone system has been employed on a 
number of the United States war ships. It was frequently found 
that vessels 10 or 12 miles away and equipped with the wireless 
telegraph apparatus only could hear conversations between vessels 
with wireless telephone apparatus. This of course might naturally 
be expected. The McCarthy brothers, of San Francisco, informed 
the writer in 1905 that somewhat similar incidents had happened 
during experiments which they had been making with wireless 
telephony in California. 

Special tests of the De Forest wireless telephone apparatus were 
conducted by Dr. De Forest before the British Admiralty during Sep¬ 
tember, 1908. These were one-way tests, the receiving apparatus 
being on the “Vernon” training ship in Portsmouth Harbor, while 
the transmitting apparatus was on the “Furious,” which vessel 
steamed out to a distance of 50 knots from Portsmouth. During a 
period of about 9 hours the telephone was used every 15 minutes for 
the transmission of messages and stock quotations; the maximum 
distance covered being 50 knots. According to De Forest, the 
perikon detector was operative at a distance of 30 knots, but was no 
louder at that distance than the audion at 50 knots. It was found 
that the voice could be heard clearly through much interference of the 
dots and dashes of adjacent wireless telegraph stations. These favor¬ 
able results are attributed to the improved apparatus employed as 
compared with the earlier apparatus of this system. 


CHAPTER III. 


THE TELEFUNKEN, FESSENDEN, COLLINS, MARJORANA 

TELEPHONE SYSTEMS. 

TELEFUNKEN WIRELESS TELEPHONE. 

The transmitting and receiving circuits of this system are out¬ 
lined theoretically in Figs. 17 and 18, respectively. As previously 
noted, this system employs as a source of high frequency oscillations 
6 or 12 electric arcs a in series, Fig. 17, shunted with the usual 
capacity c (about .006 microfarad) and inductance I. I is also the 
coupling transformer, a is the vertical wire. M is a microphone 
transmitter. I is a wave lengthening, or tuning, coil, h is a hot 
wire ammeter in the aerial wire, e is the source of direct current, 
220 or 440 volts. Choke coils, not shown in the figure, prevent the 
high frequency oscillations from entering the dynamo circuit, r is 
a permanent resistance used to regulate the current strength of the 
arc circuit. An arrow across the inductance and capacity symbols in 
this and other figures is the conventional sign that the apparatus is 
adjustable or variable. The microphone transmitter may be placed 
across the secondary of the coupling transformer i as shown in the 
figure, or directly in the aerial. Tuning is indicated when the hot 
wire ammeter shows maximum deflection. The variations of current 
caused by the microphone transmitter m when spoken into are also 
observable in the ammeter h. The positive electrodes of the arcs a 
consist of a copper tube c', about 8 inches long and 2.6 inches wide; 
being concave at the bottom. This tube is kept filled with water 
which has to be renewed every 8 or 10 hours, owing to evaporation 
due to heat from the arc. Each negative electrode c consists of a 
solid carbon button, 1.2 inches in diameter, placed in the curved space 
at the bottom of the tube. The carbon in burning shapes itself to 
this space. The amount of carbon consumed in each arc is about half 
an inch in 300 hours. The copper is not materially affected by the 

24 


TELEFUNKEN WIRELESS TELEPHONE. 25 

arc. The space between the electrodes in operation is very short, 
about one-eighth of an inch. Each pair of electrodes may be brought 
together and adjusted independently. The entire series of arcs (6 
or 12, depending on whether 220 or 440 volts are utilized) are held 
together by a suitable clamp, by which they may be advanced or 
withdrawn simultaneously. By pressing the clutch forward for an 
instant, thereby closing the spark gap, the electrodes are set at the 
required distance. The arc is struck by withdrawing the carbons. 
When this adjustment is obtained the arcs generate regular oscilla¬ 
tions without further adjustment for two or three hours; in other 
words, until an unevenness in the arcs disturbs the regularity of the 
oscillations. 

Obviously considerable heat is developed in the microphone trans¬ 
mitter with the strong currents employed in wireless telephony, 
which affects the transmitter more or less detrimentally after a time. 
Hence when not in use the transmitter m is cut out of the circuit by 
a switch. 



The receiving apparatus and circuits of this system are simple, 
consisting only of a variable inductance, or variometer, L, Fig. 18, a 
thermo or electrolytic receiver d, telephone receiver t, and a capacity, 
not shown in the figure. 

The length of wave employed in this system is about 800 meters 
(2,400 feet), implying a frequency of 375,000 cycles per second. 
The energy output is about 800 watts, at 220 volts, 3.6 amperes. 
With this power speech is transmitted clearly to a distance of 25 
miles. With 440 volts and 2 amperes and employing aerials 180 feet 
high at each station, speech has been transmitted during official tests 
to a distance of 42 miles, namely between the Brooklyn Navy Yard 
and the Fire Island government stations. This is with the present 













26 


WIRELESS TELEPHONY. 


ordinary microphone transmitter. With more powerful transmitters 
it is expected that distances exceeding one hundred miles will be 
covered by this system. 

Practically all the apparatus employed in the Telefunken wireless 
telephone system may be placed on a table 3 feet long by 10 inches 
wide, as illustrated in Fig. 19. In this figure ah is an ammeter in 
the direct current circuit, h and oh are hot wire ammeters in the 
aerial wire and the oscillation circuit, respectively. M is the mouth¬ 
piece of the microphone transmitter, l is a variometer in the receiving 
aerial circuit, l is the inductance in the aerial transmitting circuit, 
i is the hinged primary of the transmitter tuning coil, s' is its 
stationary secondary in series with the aerial; c below d ' in figure, 
is a variable condenser in the transmitting circuit; d ' is a switch for 
short circuiting the telephone transmitter to prevent undue heating 
when not in use, n is a switch and fuse in the arc circuit, c 1 are the 
copper electrodes (the carbon electrodes are not visible in this fig¬ 
ure), h is a handle for regulating the arcs, s are springs on which the 

carbon electrodes 
are mounted; r, r 
are cylinders 
which control the 
length of the arcs, 
d indicates the de¬ 
tector, and connec¬ 
tions to the tele¬ 
phone receiver, etc. 
The operation of a 
switch, as in the 
case of this com¬ 
pany’s wireless tel¬ 
egraph outfit, con¬ 
nects the transmit¬ 
ting or receiving 
apparatus as de¬ 
sired with the antenna. There is no means of knowing whether 
speech transmitted is being received until the speaker pauses and 
awaits a reply from the distant station. The experience of this com¬ 
pany has thus far shown that wireless telegraph stations working 
with thp same wave lengths as the telephone station do not disturb 



Fig. 19. Telefunken Wifeless Telephone 

Apparatus. 








FESSENDEN WIRELESS TELEPHONE. 


27 


the latter unless when very near, say, within 4 miles. At 15 miles 
no disturbance is noted. 

It is stated by the Telefunken engineers that the oscillations set 
up by the foregoing arrangement of the arcs are of a much more 
uniform quality, and that the energy output is much higher than 
that of the single arc burning in hydrogen gas, even when used with 
an air blast or magnetic blow out. They report that when the 
coupling is loose and the tuning of the aerial is accurate all the 
consonants and vowels are received with equal loudness; otherwise 
the vowels a and o, which on account of their wave form are very 
suitable for transmission, are received loudly, while i and u are* 
received very faintly. Obviously therefore loose coupling and accurate 
or sharp tuning are very essential in such systems. 


THE FESSENDEN WIRELESS TELEPHONE SYSTEM. 


In Figs. 20, 21, are outlined the transmitting and receiving cir¬ 
cuits of the Fessenden wireless telephone system, g. Fig. 20, is a 1 
kilow T att alternating current generator developing 150 volts at 81,000 
cycles per second. A high-power microphone transmitter m is in 
series with the antenna a and the armature of the generator. In 
Fig. 21 i, c, D form the usual receiver oscillation circuit, d is a* 
liquid barretter, or electrolytic detector, t is a telephone receiver. 
P is a potentiometer for regulating the potential of dry battery b, to 
the critical amount required by the detector. 

In external appearance the high-power microphone transmitter 




Fig. 20. Fessenden Wireless Telephone. Theory. Fig. 21 . 

devised by Fessenden for wireless telephony, and termed the ‘Trough” 
transmitter, resembles the ordinary long-arm carbon telephone trans¬ 
mitter. The transmitter proper, as described by the inventor, con¬ 
sists of a soapstone annulus to which are clamped two metal plates 
having platinum iridium electrodes. Through a hole in the centre 











28 


WIRELESS. TELEPHONY. 


of one plate there passes a rod, attached at one end to a diaphragm 
and at the other end to a platinum iridium spade. The side electrodes 
are water jacketed. A teaspoonful of carbon granules is placed in 
the central space. It is stated that this transmitter does not pack, 
requires no adjustment, and will carry 15 amperes at 25 volts without 
impairing articulation. 

The fall of potential across the ordinary microphone transmitter 
used in the aerial wire in wireless telephony is about 5 to 15 volts 
with a current flow of about 2 amperes. The ordinary percentage 
of variation in the amplitude of the emitted oscillations produced by 
microphone transmitters in wireless telephony is about 5 per cent. 
With a condenser telephone transmitter c , Fig. 22, inserted in a 
shunt to the aerial radiating circuit, one of the plates of which is 
vibrated by speech uttered at the mouthpiece M, thereby producing 
variations of the capacity of the aerial, it is claimed that a much 
great variation of the amplitude of the oscillations is obtainable. Fes¬ 
senden has also proposed to vary the inductance of the radiating 
circuit by introducing the secondary s, Fig. 23, of a transformer t 
in the aerial, the primary p of which is in circuit with a microphone 
transmitter m and battery b. For wireless telegraph or telephone 
purposes, Fessenden has devised a sensitive telephone receiver termed 
the heterodyne. The heterodyne, indicated in Fig. 25, consists of 
two small coils, one w, fixed, the other w', movable. The fixed coil 
is wound over a core of fine iron wire; the movable coil is attached to 
a mica diaphragm m, and is held parallel with the fixed coil. A high 
frequency current, from a local source e, of relatively the same 
frequency as the transmitted oscillations, is maintained in the fixed 
coil. The movable coil is inserted in series in the aerial circuit a. 
Normally the currents in the coils do not affect the movable coil, but 
modifications of the incoming oscillations in the aerial circuit due 
to the distant microphone transmitter produce reactions between the 
two coils resulting in vibrations of the mica diaphragm corresponding 
to those of the transmitter, which vibrations are heard in the ear 
piece D as speech or other sounds. 

In order to facilitate listening in to ascertain whether messages are 
being correctly received, Fessenden provides a switch whereby the 
transmitting and receiving circuits may be quickly interchanged with 
the aerial. The same inventor also utilizes for this purpose the 
principle of the “bridge” and “differential” duplex telegraph methods. 


FESSENDEN WIRELESS TELEPHONE. 


29 

an arrangement of which is outlined in Fig. 25. Here a, b, and 
a '> b' may represent the arms of a bridge duplex. A condenser c' 
and detector d are placed in the bridge wire w. a is the usual aerial, 
c is an “artificial” aerial, g may be a source of sustained oscillations; 
M a microphone transmitter, n a battery. When speech is uttered in 
the microphone transmitter m, the amplitude of the oscillations will 
be varied by the action of the differentially arranged coils x, a.; x', a', 
etc., but when the arms of the bridge are equal, when the resistance, 
inductance, and capacity of the artificial aerial, c, equal those of a, 



Fig. 22 . Fig. 23. Fig. 24. Fig. 25. 


and the differential coils are correctly proportioned, the variations 
of amplitude due to transmitter m will not affect detector d. It will 
be responsive at the same time, however, to arriving oscillations in 
the aerial, in the manner well understood in duplex telegraph opera¬ 
tion. (See Author’s “American Telegraphy,” page 109.) In prac¬ 
tice, to further avoid disturbance from the sending oscillations, Fes¬ 
senden employs additional refinements, including an “interrupter 
preventer,” not indicated in the figure. It might, however, consist 
of the primaries of two small induction coils placed in multiple in 
the bridge wire with a condenser in series in each primary and with 
the detector in series with the secondaries of the coils, in place of 
the arrangement, c', d, shown in the bridge wire w in the figure. 

In connection with the wireless telephone experiments conducted 
by Professor Fessenden between New York and Brant Rock, it is 
reported that speech has been transmitted with an expenditure of 
less than one-third of a horse-power (200 watts). On this basis the 
experimenter concludes that with a mast 600 feet high and an ex¬ 
penditure of 10 kilowatts, it will be possible to telephone between 
America and Europe without wires. The aerial used by Fessenden 
at Brant Rock is one of the highest in existence. The mast is 420 
feet in height and consists of a steel tube 3 feet in diameter and 
maintained in a vertical position by suitable guy wires. 



















30 


WIRELESS TELEPHONY. 


COLLINS WIRELESS TELEPHONE. 

This system, Figs. 26, 27, employs as a source of continuous oscil¬ 
lations an arc with carbon disc electrodes s, s, that rotate in a mag¬ 
netic field established by the electromagnet m, m, the coils of which 
also act as choke coils, preventing the oscillations from surging back 
into the high tension generator d, driven by the motor DC. The mag¬ 
net fixes the arc in the best position for successful operation. The 
oscillation circuit comprises the arc, plate glass condensers c, c, and 
the inductance L. Tuning is effected by means of sliding contacts or 
clips n, n. Best condition of tuning is indicated by an indicating 
device consisting of an exhausted tube r, 13 inches Tong and 1.75 
inches in diameter. Platinum wires t, t, .062 inch in diameter, enter 
the tube and almost touch at the middle. Kesonance is indicated by 



a glow at the break in the wires, which glow extends further and 
further back as the strength of the oscillations increases: If the posi¬ 
tive and negative oscillations are of equal strength, the glow will 
extend an equal distance from the break in the wires; if unequal, 
the glow will be more pronounced on one side than the other. The 
arc is in shunt with a condenser c, and the secondary of a trans¬ 
former l, the primary of which is fed by a 25-volt direct current 
source E. Speech spoken into the microphone transmitter M produces 
modifications of the oscillations due to the arc. According to the 
inventor, the electromotive force of the high frequency oscillations 
is raised to about 100,000 volts in the aerial circuit, k is a tuning, 
or lengthening, coil in the aerial a. 







































MARJORANA WIRELESS TELEPHONE. 


31 ' 


The receiving circuit of this system is outlined in Fig. 27. C, c 
and l form the oscillation circuit, a is the aerial wire, d is a thermo¬ 
electric detector consisting of a “couple” of two different metals, 
crossed at right angles and below the junction of which is placed a 
resistance wire that is heated by incoming oscillations, thus producing 
variations of current in the circuit of telephone t corresponding to 
the transmitted speech waves. The strength of battery b is varied 
as desired by the rheostat or potentiometer r. Experimental tests 
have been made with this system between the Singer Building, New 
York City, and Newark, N. J. 


THE MARJORANA WIRELESS TELEPHONE SYSTEM. 

Professor Quirino Marjorana, after whom this system is named, 
has conducted a number of wireless telephone experiments in Italy. 
As a means of obtaining undamped oscillations he at first employed 
the arrangement shown theoretically in Fig. 28. An ebonite disc d, 
mounted on the shaft s of a suitable motor, carries a metal ring r, r, 
on its opposite faces. Metal brushes b, b , to which the wires of 
oscillation circuit c, n, are attached, rest on each of these rings. To 
each metal ring is fixed a steel wire w, w, 27 inches in length, parallel 
with one another, their open ends coming close together; this consti¬ 
tuting a spark gap g of the oscillation circuit. In the oscillation 
circuit is inserted also the secondary n of a transformer, the primary 
of which ft' is supplied with alternating current from a source E. 
When the motor carrying the metal rings and steel wires is rotated 
the air pressure at the spark gap g has the effect of breaking each 
principal spark into a number of minor sparks, with the result that 
about 20,000 interruptions per second are obtained. Some success 
was obtained with this device, but it was not suitable for practical 
operation. 

Subsequently Professor Marjorana adopted an arc generator of 
sustained oscillations practically similar to the Poulsen device already 
described. This arrangement is indicated in Fig. 29, in which K is a 
copper electrode, Jc a carbon electrode, burning in an atmosphere of 
hydrogen; m, m are electromagnets for steadying the position of the 
arc relative to the electrodes, thereby enhancing the efficiency and 
constancy of the oscillations. The coils of the electromagnets are 
fed by the same direct current e that feeds the arc, and they act as 



32 


WIRELESS TELEPHONY. 


choke coils to hold back the high frequency oscillations (150,000 to 
1,000,000 per second) from the source of direct current E. 

To avoid the heating troubles incidental to the use of strong cur¬ 
rents in the carbon microphone transmitter, what is termed a liquid 
transmitter, or hydraulic microphone transmitter, is utilized in this 
system. One form of this transmitter is outlined in Fig. 29. It 
consists of a tube t in which water or other suitable liquid is caused 
to flow in the direction indicated by the arrow. The tube has a 
minute opening at its lower end e out of which the liquid normally 
falls in a thin solid column for a considerable distance, when it begins 
to form into drops, as at n. Marjorana found that rapid shocks im¬ 
parted to the tube have the effect of varying the point at which drops 



Figs. 28, 29, 30. Marjorana Wireless Telephone System. 

begin to form, bringing that point nearer to the end of tube t. To 
avail of this property the tube is made of strong material except at a 
point on its side near the lower end of the tube, where a thin and 
elastic diaphragm is inserted. A cross rod r connects this diaphragm 
with the diaphragm of a telephone transmitter M. Sounds spoken 
into the mouthpiece of m have the effect of causing contractions in 
the column of water, as indicated by the dotted lines, which contrac¬ 
tions become more frequent toward the lower end of the column. 
Two small platinum wires w, w, which may form part of the aerial 
circuit a, are placed at a desired point in the water column, the 
liquid completing the circuit. The vibrations of the diaphragm due 
to the voice vary the shape and quantity of the liquid jet between the 
wires w, w, and consequently vary the resistance of the circuit; this 
modifying the transmitted oscillations in the manner desired for the 
reproduction of speech at the receiving station. Acidulated water, 
mercury or other liquids have been utilized by Marjorana in his 
experiments. 


































MARJORANA WIRELESS TESTS. 


33 


The receiving circuits, Fig. 30, are virtually similar to those de¬ 
scribed herein in connection with other wireless systems, a is the 
aerial, inductively coupled to the receiver oscillation circuit, c i& 
the usual capacity, r is a telephone receiver. A thermo-electric 
detector d has been employed by the inventor, but in his later ex¬ 
periments he reports that he finds the audion detector the most 
satisfactory; his tests with the electrolytic, the electro-magnetic de¬ 
tector, and a pair of carbon contacts were not so successful. 

It is stated that excellent results were obtained with the Marjorana 
telephone system between Monte Mario, Rome, and Messina, Sicily, 
a distance of about 300 miles, prior to the recent destruction of 
Messina by earthquake. 


In closing it may be said that, although, of course, wireless teleph¬ 
ony is still susceptible of much improvement in several directions, 
yet it cannot be fairly gainsaid that it has already reached a point 
of limited practical utility. That it may soon be available for 
general purposes is much to be desired. As the writer has noted 
elsewhere (see Transactions Association of Railway Telegraph Su¬ 
perintendents, 1907) “wireless telephony, if only available for a com¬ 
paratively short distance, obviously could be installed to advantage in 
the officer’s room of every ship that floats ocean, lake, river or har¬ 
bor,” because of the fact that telephony requires no specially trained 
operator. To attain such a result, however, it will of course be 
necessary that a degree of reliability and simplicity of apparatus be¬ 
yond that yet devised must be reached, in order that it may be readily 
manipulated by the ordinary ship’s officer. As perhaps first intimated 
by the author (see page 171, Part 1), telephoning without wires has 
the technical advantage over wire or cable telephony in that it does 
not have to contend with the static capacity of the conductor. When 
therefore the necessary improvements in this art have been made, 
perhaps in the direction of more powerful high frequency oscillations, 
and more powerful telephone transmitters, or their equivalent, are 
developed, it is possibly not beyond bounds to expect that the claims 
now made by certain enthusiastic inventors as to trans-Atlantic wire¬ 
less telephony, and which in some quarters are at present considered 
visionary, may be ultimately realized. 




®-v.; _ 


FESSENDEN WIRELESS STATION 
BRANT ROCK, MASS. 







INDEX— Part 1 


[=□ □ LHZ1 


ABC 

Air, blasts at spark gap, 67; pressure at, 
204; air chamber, 15; views of ancients 
on, 31. 

Alaska wireless circuit, 125. 

Alphabets, 2, 74, 179, 194. 

Aerials, land and shipboard, L. T. aerials, 
212, 214, 284; crude, 257; multiple, 
64, 73 142, 209 ; for receiving only, 287. 

Amateur wireless stations, 266, 267. 

Ammeter, hot wire, 103, 226, 229. 

Anchor gap, 104, 139, 161, 166, 289. 

Antenna, 209, 301; air gap at, 139, 161; 
as condenser, 36, 38, 200 ; as Hertz os¬ 
cillator, 35; capacity of, 207, 302; 

cow’s tail, 60; energy stored in, 137; 
height of, 29, 37, 65, 72, 94, 148, 156, 
209, 253; insulation of, 59, 134, 214, 
284, 287; kites, balloons for, 93, 101, 
209, 251; leading-in wires, 60, 94, 128, 
286; material of, 122, 210; mutual ac¬ 
tion between, 207, 299; potential on, 
49, 87; relation of height to signaling 
distance, 29, 37, 291; towers for, 64; 
umbrella, 112 ; weight of masts for, 59, 
122 , 124; wire netting for, 59. 

Apparatus, adjustment of, 27, 53, 70, 163, 
205, 255, 288, 306. 

Arco, 116. 

Armorl wireless system, 180. 

Artom experiments, 243. 

Atmosphere as conductor, 30, 177. 

Atmospheric electricity, 55, 73, 95, 132, 
230, 285. 

Atom, 39, 44; electrical, Clifford on, 43. 

Battery, storage, dry, 5, 29, 58, 94, 97, 

99, 186, 194, 267. 

Bellini-Tosi, 246. 

Bernstein’s experiments, 9. 

Blondel, reference to, 35, 37, 132, 211. 

Bolometer, 299. 

Braun, 95, 210; directive experiments, 242. 

Buzzer, 8, 61, 84, 193, 289. 

Call bell, 13, 57, 70, 116, 179. 

Calls, shore and ship stations, 258. 

Capacity, inductance, 35, 71, 106, 143, 
151, 162, 205, 265, 266. 

Capacity, see Condenser, 19, 20, 48, 145; 
areas, 80, 95, 210, 211; effect on ra¬ 
diation, 205; elevated, 81; how varied, 
147; metallic cage, 134; of vertical 
wires, 207; of earth, 302. 

Carbon, at contacts, 138, 162; rod resis¬ 
tances, 104. 

Cathode rays, 39, 44. 

Cement, “electrical,” 196. 

Circuits, wireless, 261, 262. 

Clarke experiments, 60, 270. 

Coherer, see Detectors, 53, 57, 61, 70, 90, 

100, 144, 145, 146, 150, 158, 163, 184, 
195, 270; Aschkinass, 68, 184; Bell, 
146; Blondell, 132; Branly, 26, 126, 
186; Braun, 100; Brown, 188; carbon, 


C D 

Duddell singing arc, 202. 

Jervis-Smith, 185; Clarke, 188; DeFor* 
est, > 141, 304; effect of magnetism on 
efficiency, 196; figure of merit, 184; 
Gavey, 188; gold-bismuth, 153; Solari, 
Castelii, 70, 290; King’s, 186; lamp 
filament, 162; Lodge, 28; oil film, 85; 
Marconi, 189; single point, 70; mag¬ 
netic metal for, 193; ring for, 100; 
Minchin, 149; microphone, 141, 162, 
168 ; operation of, 27 ; peroxide of lead, 
178; Popoff, 134; preventing arc in, 
131; regenerable, 132 ; Righi, 187 ; sen¬ 
sitiveness of, 30, 61, 90, 141, 188, 193 ; 
signaling speed with, 61, 68, 171; 
Schaefer, 69; time of operation of, 71, 
131, 171; testing, 110; Tissot, 187; 
Tomassini, 188 ; Varley carbon, 153. 

Coherence, auto, anti, 183. 

Coils: choke, 54, 57, 67, 107; Marconi, 
55 ; Fleming, 67 ; DeForest spiral, 136 ; 
induction, see Induction Coils; high fre¬ 
quency, 203. 

Condensers, 8, 20, 22, 32, 80, 97, 99, 131, 
136, 163, 194, 268, 272, 273, 276; ad¬ 
justing, 62 ; air, 208 ; at spark gap, 132 ; 
capacity, 106, 139; copper plates, 106, 
164; hydro, 164; mechanical analogy, 
18; cylinder, 63, 99; discharges, 200, 
263 ; energy stored in, 207 ; glass plate, 
66 , 76, 157, 169, 203; as shunt, 58, 82; 
paper, 194; position of in circuits, 104; 
series-multiple, object of, 106. 

Conductors, opaque to, reflectors of, elec* 
trie waves, 25, 33, 36, 37, 56, 143, 294; 
skin excitation in, 25, 279, 298. 

Contact, disintegration of, 8, 198; imper¬ 
fect, 188. 

Counterpoise, 122, 125. 

Coupling, 116 ; tight, loose, 231, 264. 

Crooke’s tube, 42, 44. 

DeForest, reference to, 138, 190, 290; 
aerophore, 241; bent antenna, 242. 

Detector, See Coherer, 68, 69, 71, 182; 
barretter, 37, 151; carborundum, 218, 
219, 220, 290; carbon type, 101; effi¬ 
ciency tests of, 197; electric eye, 21; 
electrolytic, 140, 222, 223; Fessenden, 
151; Fleming, 190, 222 ; Hertz, 23, 26 ; 
holder, 291; Hozier-Brown, 220; mag¬ 
netic, 50, 70, 73, 193, 305; Neug- 

schwender, 68; perikon, 216, 217; re¬ 
cording, 188; resistance of, 69, 71, 152 ; 
stone, 159; Shoemaker, 165; silicon, 
216, 290; sensitiveness of, 223, 225; 
thermo-electric, 116, 221; Tomassini, 

68 ; Turpain, 185; valve, 75. 

Detonator, 194, 195. 

Dielectric, 20; under pressure, 156. 

Direction localizer, Bellini-Tosi, 246; De* 
Forest, 241: Marconi, 242; Stone, 239. 

Directive wireless radiation, 238, 244, 248. 

Disc discharger, 75. 

Dolbear wireless system, 14. 












1-0 


E F G H I 

Earth, 36, 63, 210, 302; capacity, 210; 
charged surface, 297 ; curvature, 30, 59, 
294; ground plates, 60, 211. 

Edison, 10, 14, 30, 209. 

Electric oscillations, 18, 19, 22, 23, 92, 
253, 259, 299; action on filings, 26, 
193; damping, 17, 50, 118, 144, 200; 
decrement of, 120; wave-length of, 207 ; 
diagram of, 118; effect on magnetic 
hysteresis, 71, 189; effect of resistance, 
capacity, inductance on, 21, 50, 72, 203 ; 
forced, free, 47; formulae, 20, 21, 35; 
from telegraph key, 252 ; harmonic, 156; 
how varied, 46, 62 81, 299; Kelvin on, 
18; nodes and loops of, 87; period of, 
21, 23, 50; persistent, 75, 144, 227, 
232; shortest, 21. 

Electric waves, 21, 32, 185, 259, 260, 
263; detectors of, 182; extraneous, 56, 
57, 132, 195 ; effect of ultra violet waves 
on, 73, 90; frequency, 21, 35, 53, 87, 
94, 98, 143, 147, 207, 298; on wires, 
33, 36, 300; propagation, radiation, 25, 
29, 31, 34, 38, 96, 293, 305; sliding 
wave theory, 31, 38, 96, 149, 300; in¬ 
tensity of, 34, 37, 38. 

Electrolysis, laws of, 43. 

Electromagnetic disturbances, 294; sha¬ 
dow, 301; theory of light, 17; waves, 
260, 263. 

Electronic theory, 39, 45, 293. 

Energy, 19, 29, 30, 33 ; absorption of, 36, 
294; cumulative, 38; to affect coherer, 
etc., 184, 259, 293. 

Erg, 20, 196, 197. 

Ether, 30, 31, 43, 45, 259, 293; model, 
303. 

Evershed, relay, 12. 

Faraday, references to, 6, 43. 

Feddersen, oscillations, 300. 

Fessenden, barretter, 123, 154, 204. 

Figure of merit, 184. 

Fire alarm system, 256. 

Fog horn signals, 60, 141, 179, 306. 

Franklin’s fluid theory, 41. 

Frequency of generators, 202, 228. 

Frequency meter, 113. 

Galvanometers, 4, 26, 81, 225. 

Gordon on Maxwell’s theory of light, 18. 

Gray’s transmitting key, 77. 

Ground, See Earth ; discs, 76. 

Grouped signals, 51; oscillations, 151. 

Guy wires, 122, 172. 

Harmonic system, Gray’s, 51. 

Hayes-Cram radiophone, 175. 

Henry’s experiments, 6. 

Heaviside, 32, 298. 

Heliography, 4, 251. 

Helmholtz, 43. 

Hertz, experiments, 21, 25; oscillator, 32, 
35, 36, 38; reference to, 30, 34, 162, 
297, 301, 302. 

Hertzian waves, 15 ; tapping, 61. 

Hewitt interrupter, 201. 

High power stations, 112, 159, 214. 

Image theory, 35. 

Inductance, 19, 150; as inertia, 39; coils, 
63, 67, 81, 88, 150, 156, 159; of 

transformer, 132; in centimeters, 106; 
in microhenrys, 281; formula for calcu¬ 
lating, 279. 

Induction coil, 7, 9, 14, 27, 58, 61, 80, 


84, 93, 94, 98, 130, 132, 135, 148, 
151, 156, 194, 197 ; construction and re¬ 
sistance of, 7, 66, 194, 197, 203, 274, 
276; currents employed with, 23, 202; 
strength of defined, 7. 

Induction telegraphy, 6. 

Insulators: insulation, leading-in wires, 
60, 286; guy wires, 208; of antenna, 
59, 162, 210, 287 ; split insulators, 287. 

Interrupters, 8, 58, 91, 93, 99, 155, 211; 
electrolytic, 95, 99, 198 ; hammer, 198 ; 
Lodge-Muirhead, 80; magnetic, 8, 198; 
mercury, 9, 133, 198 ; rate of vibration, 
23, 84, 91, 92, 198, 199. 

Jackson experiments at sea, 210, 254. 

Jigger, 55, 62. 

Joule, 207. 

Kelvin, reference to, 18, 50, 297. 

Kennedy, Kennelly, theories, 293, 295. 

Key, Braun, 95, 101; DeForest, 135, 137; 
Ducretet, 133; Fessenden, 151, 154; 
Fleming, 67; Gray, 78; magnetic blow 
out, 93; Marconi, 57, 58, 61, 76, 78; 
multiple break, 157, 160; Shoemaker, 
162, 164, 268 ; mercury contact, 125. 

Koepsel, on wave-lengths, 207; theory, 
302. 


Lamp, searchlight, visibility, 177, 295. 

Lecher system, etc., 36, 143, 207, 303. 

Listening in, 289. 

Lodge, reference to, 36, 37, 38, 40, 44, 
303; syntonic systems, 75. 

Lodge-Muirhead system, 83, 84. 

Long distance signaling, 30, 65, 73, 129, 
147, 253, 256, 258. 

Magnets, 70, 71, 90, 91. 

Magnetic, blow outs, 93, 101; decoherer, 
161, 187, 188 ; metals for coherers, 193 ; 
interrupters, 8, 198; ring for coherer, 
100 . 

Marconi, references, 48, 54, 56, 58, 254; 
switch, 164; bent antenna, 242 ; experi¬ 
ments, 29, 48, 72, 295; stations, 59, 
64, 74, 207, 209. 

Masts, 179 ; weight of, 59. 

Maxwell, references to, 17, 32, 39, 299. 

Mercadier, monotelephone, 51. 

Mercury, coherer, 70; contact, 181; ful¬ 
minate of, 195; switch, 81. 

Microphone, 167, 205; 188; 175, 179. 

Mirror, earth as, 35. 

Molybdenum, 216. 

Motor generator, 103, 135. 

Multiplex system, 118, 155, 160. 

Nauen station, 112. 

Newton, reference to, 34, 45. 

Oil, condensers, 66, 208; in coherers, etc.* 
53, 85, 98, 203. 

Ondegram, scope, 182. 

Orling, reference to, 142. 

Oscillating currents, 259, 301. 

Oscillator, 22, 30, 32, 35, 194, 203; Lebe- 
dew, 204; Righi, 52. 

Oscillation, circuits, 22, 65, 136, 151, 155; 
158; closed, open, 49, 95, 261; gener¬ 
ators, 75, 115, 118, 119, 121; trans¬ 
former, 278, 279, 280. 

Oscillations, See Electric Oscillations. 

Oscillophone, 168. 


P Q R S 

Parallelogram of forces, 247. 

Phase difference, 239. 

Pickard experiments, 214, 225. 

Photoelectric phone, 176; recorder, 111. 

Polarized relay, 50, 90. 

Polonium, 45. 

Popoff, 18, 27, 134. 

Portable outfits, 93, 101, 123. 

Potential indicator, 207. 

Poynting, reference to, 32, 36. 

Practical suggestions, 306. 

Preece, induction telegraph, 11. 

Protyle, 43, 45. 

Quartz, transparent to waves, 173. 

Quenched spark, 115. 

Kadiation, 25, 30, 44, 295, 303. 

Radiator, 48, 81, 144, 191. 

Radioactive matter, 45. 

Radiogoniometer, 246. 

Rays, alpha, etc., 44, 45. 

Rayleigh, reference to, 199, 205. 

Rectifiers, alternating current, 214, 215; 
critical point of, 216. 

Registers, 54, 57, 99, 128, 196, 310. 

Relay, 12, 54, 61, 91, 93; Allstrom, 226; 
current required, etc., 88, 132 ; Hughes, 
193; repeating, 131; Shoemaker, 129; 
time operation, 131, 171; Sullivan, 227; 
resonance, 117. 

Righi oscillator, 52. 

Rutherford, reference to, 45, 189. 

Scholl, Dr., 252. 

Schuster, speaking arc, 178. 

Sea water, 34, 37, 251, 294, 300. 

Selective signaling, 51, 79, 253, 303. 

Selenium cells, 174, 176, 177, 178. 

Semaphore, signaling, 3. 

Shipboard outfits, 13, 59, 93, 142. 

Shoemaker wireless system, 156. 

Siebt, Dr., reference to, 206. 

Signaling distance, 49, 73, 82, 91, 93, 94, 
119, 133, 134, 150, 156, 163, 169, 170, 
179, 190, 193, 211, 214, 215; effect of 
temperature, over frozen earth, 150; 
formula, 29 ; impeded by mineral cliffs, 
254; in warfare, 251; Morse methods 
of, 10, 53, 54, 61, 64, 95, 173, 308; 
overland, 251; speaking light, 176; 
speed of, 61, 68, 72, 127, 171; trans¬ 
atlantic, 72, 256, 295; variation in, 

253 ; by ultra violet rays, 172; whistle, 
60. 

Signal Corps circuit, Alaska, 125. 

Signals, danger, etc., 257, 258. 

Singing spark system, 115, 118. 

Siphon, 180; recorder, 83, 85, 193, 219, 
264. 

Siren, electric, 13, 253. 

Sliding contacts, 76, 92, 162, 234, 235, 
304. 

Sliding wave theory, 31, 35, 37, 300. 

Solenoids, 151. 

Sound, 15, 16, 23, 43, 188. 

Spark gap, air pressure at, 156, 173, 204; 
balls, knobs, rods, size of, 28, 53, 80, 
105, 115, 167, 268; discs at, 138, 205; 
temperature, resistance at, 50, 178; heat 
at, length. 30, 75, 137, 204, 205; noise 
at, 67, 93, 137, 205; in oil, 53; mul¬ 
tiple, 105, 157, 199. 

Speaking arc light, 175, 177, 140. 

Station calls, 258. 

Stone, wireless system, 57, 58, 162. 

Stonev, Dr. J.. reference to, 43. 

Sulphuric acid, resistance of, 192, 293. 


S T U V W 

Switches, 57, 58, 81, 99, 104, 109, 142, 
153, 192, 293. 

Synchronous systems, 163, 304. 

Syntony, 17, 47, 93, 137, 253. 

Table of wave lengths, 293. 

Tapper for coherer, 27, 28, 54, 61; mag¬ 
netic, 161, 176; manual, 195; reading 
signals by, 196. 

Taylor, reference to, 31, 35. 

Telefunken wireless, 102. 

Telegraphing from trains, 10, 12, 114, 252. 

Telemeter, 188. 

Telephone, induction telegraphy, 12, 14; 
monotone, 51; damped vibrations in, 
17; receiver, 91, 101, 139, 141, 151, 
181, 271; sensitiveness of, 224. 

Theory, Eichhorn, 232 ; Fleming, 222. 

Thermostat, 256. 

Thompson, Prof. S. P., model, 301. 

Thomson, Dr. J. J., 40, 41, 43, 44. 

Thorium, reference to, 45. 

Torpedo boats, dirigible, 196. 

Transformer, 49, 103, 108, 156, 227, 235; 
auto, 205; cycles per second, 228; 
hinged, 108; open, closed cores, 228; 
resistance of, 203; resonance in, 227, 
229, 231; series multiple, 113; step-up, 
65, 136, 198, 201, 203; power, 276. 

Tuned circuits, 47, 50, 62. 

Tuning, 40, 70, 89 ; baretter in, 38 ; mag¬ 
netic detector in, 71; grid, 150; notes 
on, 288 ; sharpness of, 223; varying ca¬ 
pacity and inductance for, 62, 67, 81, 
88, 137, 206. 

Tuning coil, 92, 234; construction of, etc., 
277, 279, 280, 281. 

Tuning fork, 16, 23, 50, 87, 264; persist¬ 
ent vibrator, 46. 

Turpain resonator, 185. 

Ultra violet rays, 73, 80, 172, 174. 

Uranium, 45. 

Varley, 153. 

Variometers, 107, 235, 282. 

Vibrations, superposed, etc., 156, 179; 
155, 299, 303. 

Voltmeter, hot wire tests, 66. 

Von Lepel wireless system, 119. 

Watt, kilowatts, 29, 30, 267. 

Wave chute, 149, 211. 

Wave meters, 282, 313. 

Wave-lengths, 75, 104, 206, 231; plotting, 
232; motion, simple, 238, 240; trains, 
persistent, 156; undulations, diagram of, 
237; varying, 116. 

Weeding out circuits, 158. 

Wildman, reference to, 125. 

Wind, moist, effect of on charge, etc., 125. 

Wireless telegraph systems, Armorl, 180; 
Branly-Popp, 127; Braun, 95; Bull, 
304; Clark, 124, 211; DeForest, 107; 
Dolbear, 14; Ducretet-Popoff, 133 ; Ed¬ 
ison, 14; Ehret, 303; Fessenden, 149; 
Guarini, 129, 256; heliograph, 4, 308; 
Hozier-Brown, 220; induction, 10; 
Lodge-Muirhead, 79; Marconi. 52, 75; 
Massie, 166 : Ruhmer, 176 ; Slaby-Arco, 
87; Shoemaker, 156; Stone, 126: Tele- 
funken, 102; Von Lepel, 119; Zickler, 
172. 

Wireless telegraphy, automobiles in, 129, 
148; early experiments, 26, 29; effect 
of lightning on, 254; exploding mines 


w 


w z 


by, 195; for fog signals, 179; moving 
trains, 10, 252; notes on, 251; inter¬ 
ference with, 253; fire alarm, 256; in 
warfare, 250; on vessels, 93, 250; oper¬ 
ation of, 27, 53, 61, 63, 70, 84, 90, 91, 
163, 205, 305; practical applications of, 
250; reliability of, 253, 305; skill in 
handling apparatus, 254; various appli¬ 
cations of, 255; suggestions on learning 
to signal by, 255, 306. 


Wireless telephone systems, Armorl, 181 
Bell, 174; Collins, 178; Hayes-Cram, 
175; Ruhmer, 176; Simon, 171; See 
Part 2. 

Wireless telephony, 255. 

Wires, vertical, See Antenna. 

Zeeman, 43. 

Zenneck, reference to, 210. 

Zincite, perikon, 218. 


INDEX— Part 2 


A-L 

Arc, or machine generators of sustained 
oscillations, 13, 19, 20, 24; striker, 21; 
arcs in series, 13, etc. 

Audion, 20. 

Brant Rock station, aerial, 4, 29. 

Bridge, differential device, 29. 

British Admiralty tests, 23. 

Buzzer, or chopper, 21. 

Campos, reference to, 12. 

Carbon electrode, rotating, 7. 

Detectors, restoring action limit, 13; in 
wireless telephony, 12, 13, 27. 

Disc dischargers, 9, 10. 

Distance of telephone transmission, 18, 25. 
Duddell’s singing arc, 4, 5. 

Eiffel Tower wireless station, 23. 
Electromotive force on aerial, 30. 

Fessenden, 4, 12; heterodyne, 28; tele¬ 
phone, 24. 

Frequency necessary for speech, freques, 3. 
Glace Bay station, 10. 

Heterodyne, 28. 

Hozier-Brown oscillation generator, 8. 
Hydraulic transmitter, 29. 

Interrupter preventer, 29. 

Jigs, 3. 

Kennelly, reference to, 3. 

Listening-in device, 28. 


M-W 

♦ 

Machine oscillation generator, 8. 

Marjorana, 13; wireless telephone, 31. 

McCarthy brothers, reference to, 23. 

Microphone transmitter, 19, 22, 24, 27, 28. 

Oscillating arc, 6, 7. 

Oscillations, 2; capacity in circuit, 12; 
current for, 12 ; damped, 3, 5 ; generator, 
8, 10, 31; interval between, 3; means 
of modifying, 12; notes on, 11; not 
continuous, 10; oscillation vs. spark 
method of signaling, 14; sustained, 3, 
20; weak magnetic effects of low, 6. 

Pancake tuner, 22. 

Perikon detector, 22. 

Poulsen, 14, 18 ; arc generator, 31; wire* 
less telephone, 15, 16 ; stations, 17. 

Ruhmer wireless telephone, 15. 

Shoemaker, reference to, 11. 

Telefunken wireless telephone, 13. 

Thermo-electric detectors, 31, 33. 

Thomson, reference to, 7. 

Von Lepel oscillator, 10. 

Wave-lengths, 18. 

Wireless telephony, 7; Collins, 30; De- 
Forest, 19; Fessenden, 24; Marjorana, 
31; Poulsen, 16; Ruhmer, 15; effect of 
nearby wireless telegraph stations on, 
27; long distance experiments with, 
utility of, 33. 



1909 —NEW AND ENLARGED EDITION—1909 


American Telegraphy and Encyclopedia of the Telegraph 

SYSTEMS—APPARATUS-OPERATION 

by- 

william MAVER, Jr., 

Ex-Electrician Baltimore and Ohio Telegraph Company, Member American Institute 
of Electrical Engineers, Author Movers Wireless Telegraphy. 

One Volume, Cloth, 656 Pages, 490 Excellent Diagrams and Illustrations. 

“ A book for Electricians, for Electrical Workers, for Students of Electricity. No 
mathematics. As useful in the Power House as in the Telegraph Office. Used as 
a hand-book in all the principal Telegraph and Telephone Electrical Departments, 
and as a text-book on Telegraph Engineering in many of the colleges of this coun¬ 
try, and by the Signal Corps of the United States Army. Every subject treated in 
full detail and in the simplest possible language.” 

This work contains at least 22 books in one on Electricity, Telegraphy and 
Telegraph Engineering. The following is a brief summary of the subjects treated: 

Elementary Electricity and Magnetism, Primary and Stor¬ 
age Batteries, Dynamos and Motors, etc. 53 Pages, 33 Illustrations. 

Electrical Testing, Wheatstone Bridge, Line Testing, Wire 
and Cable Testing for Conductivity and Insulation 
Resistance, Localizing Faults in Wires and Cables, 
etc. No other book necessary for practical results.... 40 
The Condenser, Rheostat, Inductance, Capacity, Imped¬ 
ance, Galvanometers, etc. 37 

Morse Telegraphy and Apparatus, Alphabets, etc. 48 

Automatic Telegraph Repeaters, twenty-four different re¬ 
peaters described. 35 

Duplex and Quadruplex Telegraphy, theory, practical 

management of, etc. 50 

Wireless Telegraphy, Marconi, De Forest Systems, Theory, 

etc. 

Simultaneous or Composite Telegraphy and Telephony, 

Edison Phonoplex, Time Telegraph Service, etc.. 

Submarine Telegraphy, showing arrangement of siphon 

recorders, cable relays, artificial cables, etc.... 20 

Automatic Telegraphy, Wheatstone System, Writing Tele¬ 
graphy, Telautograph, Gray’s Harmonic System, etc., 50 
Military and Naval Telegraph Signaling, Station and 

Field Kits, Codes, etc... 

Printing Telegraphy, including Stock Tickers, etc. 

American District Telegraph Service, Apparatus and Oper¬ 
ation, etc... 

Burglar Alarm Telegraph Systems, Holmes, Wilder Sys¬ 
tems, etc... 

Fire Alarm Telegraph Systems, Auxiliary, Automatic, etc., 

Police Patrol and Municipal Telegraph Systems, Tele¬ 
graph and Telephone. 

Railroad Block Signal Systems, Miller Cab Signal, etc.... 

Manufacture of W^ire, Construction and Maintenance of 
Telegraph Lines—Overhead, Underground, Subma¬ 
rine Cables, Conduits, etc., tables, etc. 54 

Including all the important systems of Telegraphy employed in the United 
States, Canada, Mexico, South America, Great Britain, Australia and New Zealand. 

Sent postpaid to any part of the world, $5.00. 


40 

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37 

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28 

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MAVER’S 


WIRELESS TELEGRAPHY AND TELEPHONY: 


A HANDBOOK OF, 


8vo, t Cloth, 366 Pages, 258 Illustrations. Price $3 postpaid. 


MAVER PUBLISHING COMPANY. 136 Liberty St., New York. 


MAVER ELECTRICAL SUPPLY CO. 

136 Liberty Street, New York. 

Wireless Telegraph Apparatus for Practical and Experimental Use. 

ELECTRICAL APPARATUS AND SUPPLIES, WET AND DRY BATTERIES, ETC. 


W M. MAVER, Jr. 

Consulting Electrical Engineer. Member Am. Inst. Elec. Engineers, 

136 LIBERTY STREET, NEW YORK. 

Investigations and Reports on Telegraphy, Telephony, Wireless Teleg¬ 
raphy and Telephony, Insulating Materials, Wires, Underground Cables arid 
Conduits, etc. 



















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